@unpublished{HenkelPieplow2014,
  author    = {Henkel, Carsten and Pieplow, Gregor},
  title     = {Reply to Comment on 'Fully covariant radiation force on a polarizable particle'},
  series = {New journal of physics : the open-access journal for physics},
  volume    = {16},
  journal   = {New journal of physics : the open-access journal for physics},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/16/11/118002},
  pages     = {8},
  year      = {2014},
  abstract  = {We argue that the theories of Volokitin and Persson (2014 New J. Phys. 16 118001), Dedkov and Kyasov (2008 J. Phys.: Condens. Matter 20 354006), and Pieplow and Henkel (2013 New J. Phys. 15 023027) agree on the electromagnetic force on a small, polarizable particle that is moving parallel to a planar, macroscopic body, as far as the contribution of evanescent waves is concerned. The apparent differences are discussed in detail and explained by choices of units and integral transformations. We point out in particular the role of the Lorentz contraction in the procedure used by Volokitin and Persson, where a macroscopic body is 'diluted' to obtain the force on a small particle. Differences that appear in the contribution of propagating photons are briefly mentioned.},
  language  = {en}
}
@article{FolmanKruegerSchmiedmayeretal.2002,
  author    = {Folman, R. and Kr{\"u}ger, P. and Schmiedmayer, J{\"o}rg and Denschlag, J. H. and Henkel, Carsten},
  title     = {Microscopic atom optics : from wires to an atom chip},
  year      = {2002},
  abstract  = {We review the 10 year long journey into the miniaturization and integration of matter wave optics resulting in devices mounted on surfaces, so called atom chips. The first experiments started with the guiding of atoms with free standing wires and investigated the trapping potentials in simple geometries. Atom optical elements can now be micro fabricated down to 1 um size on atom chips. The creation of a Bose-Einstein condensate miniaturized in surface traps was recently achieved, and the first attempts to integrate light optics are in progress. In this review, we describe microscopic atom optics elements using current carrying and charged structures. Experiments with free standing structures (atom wires)are reviewed, investigating the basic principles of microscopic atom optics. We then discuss the miniaturization on the atom chip. One of the open central questions is dealt with: what happens with cold atoms close to a warm surface, how fast will they heat up or lose their coherence? The review concludes with an outlook of what we believe the future directions to be, and what can be hoped for.},
  language  = {en}
}
@article{HenkelWallisWestbrooketal.1999,
  author    = {Henkel, Carsten and Wallis, H. and Westbrook, N. and Aspect, Alain and Sengstock, K. and Ertmer, W.},
  title     = {Theory of atomic diffraction from evanescent waves},
  year      = {1999},
  abstract  = {We review recent theoretical models and experiments dealing with the diffraction of neutral atoms by a reflection grating, formed by a standing evanescent wave. We analyze diffraction mechanisms proposed for confront the theory with experiment.},
  language  = {en}
}
@article{RogobeteSchnieppSandoghdaretal.2003,
  author    = {Rogobete, Lavinia and Schniepp, H. and Sandoghdar, Vahid and Henkel, Carsten},
  title     = {Spontaneous emission in nanoscopic dielectric particles},
  issn      = {0030-3992},
  year      = {2003},
  language  = {en}
}
@phdthesis{Henkel2004,
  author    = {Henkel, Carsten},
  title     = {Coherence theory of atomic de Broglie waves and electromagnetic near fields},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001272},
  school      = {Universit{\"a}t Potsdam},
  year      = {2004},
  abstract  = {Die Arbeit untersucht theoretisch die Wechselwirkung neutraler Teilchen (Atome, Molek{\"u}le) mit Oberfl{\"a}chen, soweit sie durch das elektromagnetische Feld vermittelt wird. Spektrale Energiedichten und Koh{\"a}renzfunktionen werden hergeleitet und liefern eine umfassende Charakterisierung des Felds auf der sub-Wellenl{\"a}ngen-Skala. Die Ergebnisse finden auf zwei Teilgebieten Anwendung: in der integrierten Atomoptik, wo ultrakalte Atome an thermische Oberfl{\"a}chen koppeln, und in der Nahfeldoptik, wo eine Aufl{\"o}sung unterhalb der Beugungsbegrenzung mit einzelnen Molek{\"u}len als Sonden und Detektoren erzielt werden kann.},
  language  = {en}
}
@misc{HenkelSteaneKaiseretal.1994,
  author    = {Henkel, Carsten and Steane, Andrew M. and Kaiser, Robin and Dalibard, Jean},
  title     = {A modulated mirror for atomic interferometry},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42279},
  year      = {1994},
  abstract  = {A novel atomic beam splitter, using reflection of atoms off an evanescent light wave, is investigated theoretically. The intensity or frequency of the light is modulated in order to create sidebands on the reflected de Broglie wave. The weights and phases of the various sidevands are calculated using three different approaches: the Born approximation, a semiclassical path integral approach, and a numerical solution of the time-dependent Schrdinger equation. We show how this modulated mirror could be used to build practical atomic interferometers.},
  language  = {en}
}
@misc{HenkelCourtoisAspect1994,
  author    = {Henkel, Carsten and Courtois, Jean-Yves and Aspect, Alain},
  title     = {Atomic diffraction by a thin phase grating},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42269},
  year      = {1994},
  abstract  = {We present a semiclassical perturbation method for the description of atomic diffraction by a weakly modulated potential. It proceeds in a way similar to the treatment of light diffraction by a thin phase grating, and consists in calculating the atomic wavefunction by means of action integrals along the classical trajectories of the atoms in the absence of the modulated part of the potential. The capabilities and the validity condition of the method are illustrated on the well-known case of atomic diffraction by a Gaussian standing wave. We prove that in this situation the perturbation method is equivalent to the Raman-Nath approximation, and we point out that the usually-considered Raman-Nath validity condition can lead to inaccuracies in the evaluation of the phases of the diffraction amplitudes. The method is also applied to the case of an evanescent wave reflection grating, and an analytical expression for the diffraction pattern at any incidence angle is obtained for the first time. Finally, the application of the method to other situations is briefly discussed.},
  language  = {en}
}
@article{PuhlmannHenkelHeueretal.2016,
  author    = {Puhlmann, Dirk and Henkel, Carsten and Heuer, Axel and Pieplow, Gregor and Menzel, Ralf},
  title     = {Characterization of a remote optical element with bi-photons},
  series = {Physica scripta : an international journal for experimental and theoretical physics},
  volume    = {91},
  journal   = {Physica scripta : an international journal for experimental and theoretical physics},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0031-8949},
  doi       = {10.1088/0031-8949/91/2/023006},
  pages     = {113 -- 114},
  year      = {2016},
  abstract  = {We present a simple setup that exploits the interference of entangled photon pairs. 'Signal' photons are sent through a Mach-Zehnder-like interferometer, while 'idlers' are detected in a variable polarization state. Two-photon interference (in coincidence detection) is observed with very high contrast and for significant time delays between signal and idler detection events. This is explained by quantum erasure of the polarization tag and a delayed choice protocol involving a non-local virtual polarizer. The phase of the two-photon fringes is scanned by varying the path length in the signal beam or by rotating a birefringent crystal in the idler beam. We exploit this to characterize one beam splitter of the signal photon interferometer (reflection and transmission amplitudes including losses), using only information about coincidences and control parameters in the idler path. This is possible because our bi-photon state saturates the Greenberger-Yelin-Englert inequality between contrast and predictability.},
  language  = {en}
}
@article{HannemannWegnerHenkel2021,
  author    = {Hannemann, Mandy and Wegner, Gino and Henkel, Carsten},
  title     = {No-slip boundary conditions for electron hydrodynamics and the thermal Casimir pressure},
  series = {Universe : open access journal},
  volume    = {7},
  journal   = {Universe : open access journal},
  number    = {4},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2218-1997},
  doi       = {10.3390/universe7040108},
  pages     = {20},
  year      = {2021},
  abstract  = {We derive modified reflection coefficients for electromagnetic waves in the THz and far infrared range. The idea is based on hydrodynamic boundary conditions for metallic conduction electrons. The temperature-dependent part of the Casimir pressure between metal plates is evaluated. The results should shed light on the "thermal anomaly," where measurements deviate from the standard fluctuation electrodynamics for conducting metals.},
  language  = {en}
}
@article{DikovskySokolovskyZhangetal.2009,
  author    = {Dikovsky, Valery and Sokolovsky, Vladimir and Zhang, Bin and Henkel, Carsten and Folman, Ron},
  title     = {Superconducting atom chips : advantages and challenges},
  issn      = {1434-6060},
  doi       = {10.1140/epjd/e2008-00261-5},
  year      = {2009},
  abstract  = {Superconductors are considered in view of applications to atom chip devices. The main features of magnetic traps based on superconducting wires in the Meissner and mixed states are discussed. The former state may mainly be interesting for improved atom optics, while in the latter, cold atoms may provide a probe of superconductor phenomena. The properties of a magnetic side guide based on a single superconducting strip wire placed in an external magnetic field are calculated analytically and numerically. In the mixed state of type II superconductors, inhomogeneous trapped magnetic flux, relaxation processes and noise caused by vortex motion are posing specific challenges for atom trapping.},
  language  = {en}
}
@misc{HenkelCourtoisKaiseretal.1994,
  author    = {Henkel, Carsten and Courtois, Jean-Yves and Kaiser, Robin and Westbrook, C. and Aspect, Alain},
  title     = {Phase shifts of atomic de Broglie waves at an evanescent wave mirror},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42289},
  year      = {1994},
  abstract  = {A detailed theoretical investigation of the reflection of an atomic de Broglie wave at an evanescent wave mirror is presented. The classical and the semiclassical descriptions of the reflection process are reviewed, and a full wave-mechanical approach based on the analytical soution of the corresponding Schr{\"o}dinger equation is presented. The phase shift at reflection is calculated exactly and interpreted in terms of instantaneous reflection of the atom at an effective mirror. Besides the semiclassical regime of reflection describable by the WKB method, a pure quantum regime of reflection is identified in the limit where the incident de Broglie wavelength is large compared to the evanescent wave decay length.},
  language  = {en}
}
@article{ZuritaSanchezHenkel2006,
  author    = {Zurita-S{\´a}nchez, Jorge R. and Henkel, Carsten},
  title     = {Lossy electrical transmission lines: Thermal fluctuations and quantization},
  issn      = {1050-2947},
  doi       = {10.1103/Physreva.73.063825},
  year      = {2006},
  abstract  = {We present a theoretical framework for the analysis of the statistical properties of thermal fluctuations on a lossy transmission line. A quantization scheme of the electrical signals in the transmission line is formulated. We discuss two applications in detail. Noise spectra at finite temperature for voltage and current are shown to deviate significantly from the Johnson-Nyquist limit, and they depend on the position on the transmission line. We analyze the spontaneous emission, at low temperature, of a Rydberg atom and its resonant enhancement due to vacuum fluctuations in a capacitively coupled transmission line. The theory can also be applied to study the performance of microscale and nanoscale devices, including high-resolution sensors and quantum information processors},
  language  = {en}
}
@article{HenkelJoulain2006,
  author    = {Henkel, Carsten and Joulain, Karl},
  title     = {Electromagnetic field correlations near a surface with a nonlocal optical response},
  issn      = {0946-2171},
  doi       = {10.1007/s00340-006-2219-9},
  year      = {2006},
  abstract  = {The coherence length of the thermal electromagnetic field near a planar surface has a minimum value related to the nonlocal dielectric response of the material. We perform two model calculations of the electric energy density and the field's degree of spatial coherence. Above a polar crystal, the lattice constant gives the minimum coherence length. It also gives the upper limit to the near field energy density, cutting off its 1/z(3) divergence. Near an electron plasma described by the semiclassical Lindhard dielectric function, the corresponding length scale is fixed by plasma screening to the Thomas-Fermi length. The electron mean free path, however, sets a larger scale where significant deviations from the local description are visible},
  language  = {en}
}
@article{DikovskyJaphaHenkeletal.2005,
  author    = {Dikovsky, V. and Japha, Y. and Henkel, Carsten and Folman, R.},
  title     = {Reduction of magnetic noise in atom chips by material optimization},
  year      = {2005},
  abstract  = {We discuss the influence of the material type in metal wires to the electromagnetic fluctuations in magnetic microtraps close to the surface of an atom chip. We show that significant reduction of the magnetic noise can be achieved by replacing the pure noble metal wires with their dilute alloys. The alloy composition provides an additional degree of freedom which enables a, controlled reduction of both magnetic noise and resistivity if the atom chip is cooled. In addition, we provide a careful re-analysis of the magnetically induced trap loss observed by Yu-Ju Lin et al. [Phys. Rev. Lett. 92 050404 (2004)] and find good agreement with an improved theory},
  language  = {en}
}
@article{Henkel2005,
  author    = {Henkel, Carsten},
  title     = {Nanometer scala electromagnetic field fluctuations accepted for publication},
  isbn      = {1-588-83042-X},
  year      = {2005},
  language  = {en}
}
@article{HenkelGardinerNegretti2004,
  author    = {Henkel, Carsten and Gardiner, Simon A. and Negretti, Antonio},
  title     = {(De)coherence physics with condensates in microtraps},
  issn      = {1054-660X},
  year      = {2004},
  abstract  = {We discuss the dynamics of a condensate in a miniaturized electromagnetic trap formed above a microstructured substrate. Recent experiments have found that trap lifetimes get reduced when approaching the substrate because atoms couple to thermally excited near fields. The data agree quantitatively with our theory [Appl. Phys. B 69, 379 (1999)]. We focus on the decoherence of a quantum degenerate gas in a quasi-one-dimensional trap. Monte Carlo simulations indicate that atom interactions reduce the condensate decoherence rate. This is explained by a simple theory in terms of the suppression of long-wavelength excitations. We present preliminary simulation results for the adiabatic generation of dark solitons},
  language  = {en}
}
@article{ZhangHenkelHalleretal.2005,
  author    = {Zhang, B. and Henkel, Carsten and Haller, E. and Wildermuth, S. and Hofferberth, S. and Kruger, P. and Schmiedmayer, J{\"o}rg},
  title     = {Relevance of sub-surface chip layers for the lifetime of magnetically trapped atoms},
  year      = {2005},
  abstract  = {We investigate the lifetime of magnetically trapped atoms above a planar, layered atom chip structure. Numerical calculations of the thermal magnetic noise spectrum are performed, based on the exact magnetic Green function and multi layer reflection coefficients. We have performed lifetime measurements where the center of a side guide trap is laterally shifted with respect to the current carrying wire using additional bias fields. Comparing the experiment to theory, we find a fair agreement and demonstrate that for a chip whose topmost layer is metallic, the magnetic noise depends essentially on the thickness of that layer, as long as the layers below have a, much smaller conductivity; essentially the same magnetic noise would be obtained with a metallic membrane suspended in vacuum. Based on our theory we give general scaling laws of how to reduce the effect of surface magnetic noise on the trapped atoms},
  language  = {en}
}
@article{KalkbrennerHakansonSchadleetal.2005,
  author    = {Kalkbrenner, T. and Hakanson, U. and Schadle, A. and Burger, S. and Henkel, Carsten and Sandoghdar, Vahid},
  title     = {Optical microscopy via spectral modifications of a nanoantenna},
  issn      = {0031-9007},
  year      = {2005},
  abstract  = {The existing optical microscopes form an image by collecting photons emitted from an object. Here we report on the experimental realization of microscopy without the need for direct optical communication with the sample. To achieve this, we have scanned a single gold nanoparticle acting as a nanoantenna in the near field of a sample and have studied the modification of its intrinsic radiative properties by monitoring its plasmon spectrum},
  language  = {en}
}
@article{Henkel2005,
  author    = {Henkel, Carsten},
  title     = {Magnetostatic field noise near metallic surfaces},
  year      = {2005},
  abstract  = {We develop an effective low-frequency theory of the electromagnetic field in equilibrium with thermal objects. The aim is to compute thermal magnetic noise spectra close to metallic microstructures. We focus on the limit where the material response is characterised by the electric conductivity. At the boundary between empty space and metallic microstructures, a large jump occurs in the dielectric function which leads to a partial screening of low-frequency magnetic fields generated by thermal current fluctuations. We resolve a, discrepancy between two approaches used in the past to compute magnetic field noise spectra close to microstructured materials},
  language  = {en}
}
@article{HenkelJoulain2005,
  author    = {Henkel, Carsten and Joulain, Karl},
  title     = {Casimir force between designed materials : what is possible and what not},
  issn      = {0295-5075},
  year      = {2005},
  abstract  = {We establish strict upper limits for the Casimir interaction between multilayered structures of arbitrary dielectric or diamagnetic materials. We discuss the appearance of different power laws due to frequency-dependent material constants. Simple analytical expressions are in good agreement with numerical calculations based on Lifshitz theory. We discuss the improvements required for current ( meta) materials to achieve a repulsive Casimir force},
  language  = {en}
}
@article{RogobeteHenkel2004,
  author    = {Rogobete, Lavinia and Henkel, Carsten},
  title     = {Spontaneous emission in a subwavelength environment characterized by boundary integral equations},
  year      = {2004},
  abstract  = {We discuss the impact of a dielectric nanoparticle on the fluorescence light from an emitter embedded in the particle. Numerical and analytical calculations predict a slower radiative decay compared to a bulk dielectric due to electrostatic screening. We assess the relevance of the nanoparticle shape and size and the position and orientation of the molecule. The numerical results are obtained from a rigorous solution of the Maxwell equations, formulated as boundary integral equations},
  language  = {en}
}
@article{HenkelGardiner2004,
  author    = {Henkel, Carsten and Gardiner, Simon A.},
  title     = {Decoherence of Bose-Einstein condensates in microtraps},
  year      = {2004},
  abstract  = {We discuss the impact of thermally excited near fields on the coherent expansion of a condensate in a miniaturized electromagnetic trap. Monte Carlo simulations are compared with a kinetic two-component theory and indicate that atom interactions can slow down decoherence. This is explained by a simple theory in terms of the condensate dynamic structure factor},
  language  = {en}
}
@article{BoedeckerHenkelHermannetal.2004,
  author    = {Boedecker, Geesche and Henkel, Carsten and Hermann, Christian and Hess, Ortwin},
  title     = {Spontaneous emission in photonic structures : theory and simulation},
  isbn      = {3-527-40432-5},
  year      = {2004},
  language  = {en}
}
@article{Henkel2004,
  author    = {Henkel, Carsten},
  title     = {The rhysics of Atom-Surface interactions},
  year      = {2004},
  language  = {en}
}
@article{NegrettiHenkel2004,
  author    = {Negretti, Antonio and Henkel, Carsten},
  title     = {Enhanced phase sensitivity and soliton formation in an integrated BEC interferometer},
  issn      = {0953-4075},
  year      = {2004},
  abstract  = {We study the dynamics of Bose-Einstein condensates in time-dependent microtraps for the purpose of understanding the influence of the mean field interaction on the performance of interferometers. We identify conditions where the nonlinearity due to atom interactions increases the sensitivity of interferometers to a phase shift. This feature is connected with the adiabatic generation of a dark soliton. We analyse the robustness of this phenomenon with respect to thermal fluctuations, due to excited near fields in an electromagnetic surface trap},
  language  = {en}
}
@article{HenkelJoulainMuletetal.2004,
  author    = {Henkel, Carsten and Joulain, Karl and Mulet, J. P. and Greffet, Jean-Jacques},
  title     = {Coupled surface polaritons and the Casimir force},
  year      = {2004},
  abstract  = {The Casimir force between metallic plates made of realistic materials is evaluated for distances in the nanometer range. A spectrum over real frequencies is introduced and shows narrow peaks due to surface resonances (plasmon polaritons or phonon polaritons) that are coupled across the vacuum gap. We demonstrate that the Casimir force originates from the attraction (repulsion) due to the corresponding symmetric (antisymmetric) eigenmodes, respectively. This picture is used to derive a simple analytical estimate of the Casimir force at short distances. We recover the result known for Drude metals without absorption and compute the correction for weakly absorbing materials},
  language  = {en}
}
@article{HenkelNestDomokosetal.2004,
  author    = {Henkel, Carsten and Nest, Mathias and Domokos, P. and Folman, R.},
  title     = {Optical discrimination between spatial decoherence and thermalization of a massive object},
  year      = {2004},
  abstract  = {We propose an optical ring interferometer to observe environment-induced spatial decoherence of massive objects. The object is held in a harmonic trap and scatters light between degenerate modes of a ring cavity. The output signal of the interferometer permits to monitor the spatial width of the object's wave function. It shows oscillations that arise from coherences between energy eigenstates and that reveal the difference between pure spatial decoherence and that coinciding with energy transfer and heating. Our method is designed to work with a wide variety of masses, ranging from the atomic scale to nanofabricated structures. We give a thorough discussion of its experimental feasibility},
  language  = {en}
}
@article{HenkelJoulainMuletetal.2002,
  author    = {Henkel, Carsten and Joulain, Karl and Mulet, J. P. and Greffet, Jean-Jacques},
  title     = {Radiation forces on small particles in thermal near fields},
  year      = {2002},
  abstract  = {We study the optical forces due to the radiation of a thermal source. Our model consists of a particle modelled by a dipole above a half-space at temperature T. The fluctuating fields are computed using the Lifshitz model. We find two contributions to the force: a repulsive "wind" component and a dispersive force mainly due to the contribution of thermally excited surface waves. It is found that for SIC material, the latter is repulsive in the very near field. The usual van der Waals force is larger by a factor of approximately ten for submicron size particles.},
  language  = {en}
}
@article{HenkelPoetting2001,
  author    = {Henkel, Carsten and P{\"o}tting, Sierk},
  title     = {Coherent transport of matter waves},
  year      = {2001},
  abstract  = {A transport theory for atomic matter waves in low-dimensional waveguides is outlined. The thermal fluctuation spectrum of magnetic near fields leaking out of metallic microstructures is estimated. The corresponding scattering rate for paramagnetic atoms turns out to be quite large in micrometer-sized waveguides (approx. 100/s). Analytical estimate for the heating and decoherence of a cold atom cloud are given. We finally discuss numerical and analytical results for the scattering from static potential imperfections and the ensuing spatial diffusion process.},
  language  = {en}
}
@article{Henkel2001,
  author    = {Henkel, Carsten},
  title     = {Coherent transport},
  issn      = {1296-2147},
  year      = {2001},
  abstract  = {We discuss the transport of matter waves in low-dimensional waveguides. Due to scattering from uncontrollable noise fields, the spatial coherence gets reduced and eventually lost. We develop a description of this decoherence process in terms of transport equations for the atomic Wigner function. We outline its derivation and discuss the special case of white noise where an analytical solution can be found.},
  language  = {en}
}
@article{GreffetCarminatiJoulainetal.2003,
  author    = {Greffet, Jean-Jacques and Carminati, R{\´e}mi and Joulain, Karl and Mulet, J. P. and Henkel, Carsten and Mainguy, S.},
  title     = {Coherent spontaneous emission of light due to surface waves},
  issn      = {0303-4216},
  year      = {2003},
  language  = {en}
}
@article{BoedeckerHenkel2003,
  author    = {Boedecker, Geesche and Henkel, Carsten},
  title     = {All-frequency effective medium theory of a photonic crystal},
  issn      = {1094-4087},
  year      = {2003},
  language  = {en}
}
@article{HenkelKruegerFolmanetal.2003,
  author    = {Henkel, Carsten and Kr{\"u}ger, P. and Folman, R. and Schmiedmayer, J{\"o}rg},
  title     = {Fundamental limits for coherent manipulation on atom chips},
  issn      = {0946-2171},
  year      = {2003},
  language  = {en}
}
@article{GreffetCarminatiJoulainetal.2001,
  author    = {Greffet, Jean-Jacques and Carminati, R{\´e}mi and Joulain, Karl and Mulet, J. P. and Henkel, Carsten},
  title     = {Coherence properties of thermal near fields : implications for nanometer-scale radiative transfer},
  year      = {2001},
  abstract  = {With the recent development of local (optical and thermal) probe microscopy and the advent of nanotechnology, it seems necessary to revisit the old subject of coherence properies of thermal sources of light. Concerning temporal coherence, we show that thermal sources may produce quasi-monochromatic near fields. In light of this result, the possibility of perfoming near-field solid-state spectroscopy and of designing near-field infrared sources is discussed. The problem of radiative transfer between two thermal sources held at subwavelength distance is studied. The radiative flux may be enhanced by several orders of magnitude due to the excitation of resonant surface waves, and this may occur at particular frequencies. Finally, we study the spatial coherence of thermal sources and the substantial influence of the near field. Surface waves may induce long-range spatial correlation, on a scale much larger than the wavelength. Conversely, quasi-static contributions, as well as skin-layer currents, induce arbitary small correlations. With the recent development of local (optical and thermal) probe microscopy and the advent of nanotechnology, it seems necessary to revisit the old subject of coherence of thermal fields.},
  language  = {en}
}
@article{HenkelWilkens1999,
  author    = {Henkel, Carsten and Wilkens, Martin},
  title     = {Heating of trapped atoms near thermal surfaces},
  year      = {1999},
  abstract  = {We study the electromagnetic coupling and concomitant heating of a particle in a miniaturized trap close to a solid surface. Two dominant heating mechanisms are identified: proximity fields generated by thermally exicted currents in the absorbing solid and timedependent image potentials due to elastic surfaces distortions (Rayleigh phonons. Estimates for the lifetime of the trap ground state are given. Ions are paricularly sinsitive to electric proximity fields: for a silver substrate, we find a lifetime below one second at distrances closer than some ten 10^-6m to the surfaces. Neutral atoms may approach the surface more closely: if they have a magnetic moment, a minimum distance of one 10^-6m is estimatied in tight traps, the heat being transferred via magnetic proximity fields. For spinless atoms, heat is transferred by inelastic scattering of virtual photons off sorface phonons. The corresponding lifetime, however, is estimated to be extremely long compared to the timescale of typical experiments.},
  language  = {en}
}
@article{HenkelCourtois1998,
  author    = {Henkel, Carsten and Courtois, J.-Y.},
  title     = {Recoil and momentum diffusion of an atom close to a vacuum-dielectric interface},
  year      = {1998},
  abstract  = {We derive the quantum-mechanical master equation (generalized optical Bloch equation) for an atom in the vicinity of a flat dielectric surface. This equation gives access to the semiclassical radiation pressure force and the atomic momentum diffusion tensor, that are expressed in terms of the vacuum field correlation function (electromagnetic field susceptibility). It is demonstrated that the atomic center-of-mass motion provides a nonlocal probe of the electromagnetic vacuum fluctuations. We show in particular that in a circularly polarized evanescent wave, the radiation pressure force experienced by the atoms is not colinear with the evanescent wave's propagation vector. In a linearly polarized evanescent wave, the recoil per fluorescence cycle leads to a net magnetization for a Jg = 1/2 ground state atom.},
  language  = {en}
}
@article{HenkelWilkens2000,
  author    = {Henkel, Carsten and Wilkens, Martin},
  title     = {Heating of trapped particles close to surfaces-blackbody and beyond},
  year      = {2000},
  abstract  = {We discuss heating and decoherencw in traps fpr ions and neutral paricles close to metallic surfaces. We focus on simple trap geometries and compute noise spectra of thermally excited electromagnetic fields. If the trap is located in the near field of the substrate, the field fluctuations are largely increased compared to the level of the blackbody field, leading to much shorter coherence and life times of the trapped atoms. The correspinding time constants are computed for ion traps and magnetic traps. Analytical estimates for the size dependence of the noise spectrum are given. We finally discuss prospects for the coherent transport of matter waves in integrated surface waveguides.},
  language  = {en}
}
@article{HenkelSandoghdar1998,
  author    = {Henkel, Carsten and Sandoghdar, Vahid},
  title     = {Single-molecule sprectroscopy near structured dielectrics},
  year      = {1998},
  abstract  = {We present an analytical approach to the calculation of the linewidth and lineshift of an atom or molecule in the near field of a structured dielectric surface. For soft surface corrugations with amplitude lambda/50, we find variations of the linewidth in the ten percent region. More strikingly, the shift of the molecular resonance can reach several natural linewidths. We demonstrate that the lateral resolution is of the order of the molecule-surface distance. We give a semiquantitative explanation of the outcome of our calculations that is based on simple intuitive models.},
  language  = {en}
}
@article{HenkelPoettingWilkens1999,
  author    = {Henkel, Carsten and Poetting, Sierk and Wilkens, Martin},
  title     = {Loss and heating of particles in small and noisy traps},
  year      = {1999},
  abstract  = {We derive the time and loss rate for a trapped atom that is coupled to fluctuating fields in the vicinity of a room-temperature metallic and/or dielectric surface. Our results indicate a clear predominance of near-field effects over ordinary blackbody radiation. We develop a theoretical framework for both charged ions and neutral atoms with and without spin. Loss processes that are due to a transition to an untrapped internal state are included.},
  language  = {en}
}
@article{HenkelJoulainCarminatietal.2000,
  author    = {Henkel, Carsten and Joulain, Karl and Carminati, R{\´e}mi and Greffet, Jean-Jacques},
  title     = {Spatial coherence of thermal near fields},
  year      = {2000},
  abstract  = {We analyze the spatial coherence of the electromagnetic field emitted by a half-space at temperature T close to the interface. An asymptotic analysis allows to identify three different contributions to the cross-spectral density tensor in the near-field regime. It is shown that the coherence length can be either much larger or much shorter than the wavelength depending on the dominant contribution.},
  language  = {en}
}
@article{HenkelChinLangeretal.1999,
  author    = {Henkel, Carsten and Chin, Y. and Langer, Norbert and Mauersberger, R.},
  title     = {Detection of extragalactic 15N : Nitrogen nucleosynthesis and chemical evolution},
  year      = {1999},
  language  = {en}
}
@article{ChinHenkelLangeretal.1999,
  author    = {Chin, Y. and Henkel, Carsten and Langer, Norbert and Mauersberger, R.},
  title     = {The detection of extragalactic 15N : consequences for nitrogeen nucleosynthesis and chemical evolution},
  year      = {1999},
  language  = {en}
}
@article{MarzoliTombesiCiaramicolietal.2009,
  author    = {Marzoli, Irene and Tombesi, Paolo and Ciaramicoli, Giacomo and Werth, Guenther and Bushev, Pavel and Stahl, S. and Schmidt-Kaler, Ferdinand and Hellwig, Michael and Henkel, Carsten and Marx, Gerrit and Jex, Igor and Stachowska, Ewa and Szawiola, Gustaw and Walaszyk, Adrian},
  title     = {Experimental and theoretical challenges for the trapped electron quantum computer},
  issn      = {0953-4075},
  doi       = {10.1088/0953-4075/42/15/154010},
  year      = {2009},
  abstract  = {We discuss quantum information processing with trapped electrons. After recalling the operation principle of planar Penning traps, we sketch the experimental conditions to load, cool and detect single electrons. Here we present a detailed investigation of a scalable scheme including feasibility studies and the analysis of all important elements, relevant for the experimental stage. On the theoretical side, we discuss different methods to couple electron qubits. We estimate the relevant qubit coherence times and draw implications for the experimental setting. A critical assessment of quantum information processing with trapped electrons concludes the paper.},
  language  = {en}
}
@article{CarminatiGreffetHenkeletal.2006,
  author    = {Carminati, R{\´e}mi and Greffet, Jean-Jacques and Henkel, Carsten and Vigoureux, Jean-Marie},
  title     = {Radiative and non-radiative decay of a single molecule close to a metallic nanoparticle},
  issn      = {0030-4018},
  doi       = {10.1016/j.optcom.2005.12.009},
  year      = {2006},
  abstract  = {We study the spontaneous emission of a single emitter close to a metallic nanoparticle, with the aim to clarify the distance dependence of the radiative and non-radiative decay rates. We derive analytical formulas based on a dipole- dipole model, and show that the nonradiative decay rate follows a R-6 dependence at short distance, where R is the distance between the emitter and the center of the nanoparticle, as in Forster's energy transfer. The distance dependence of the radiative decay rate is more subtle. It is chiefly dominated by a R-3 dependence, a R-6 dependence being visible at plasmon resonance. The latter is a consequence of radiative damping in the effective dipole polarizability of the nanoparticle. The different distance behavior of the radiative and non-radiative decay rates implies that the apparent quantum yield always vanishes at short distance. Moreover, non-radiative decay is strongly enhanced when the emitter radiates at the plasmon-resonance frequency of the nanoparticle.},
  language  = {en}
}
@article{WestbrookHenkelWestbrooketal.1998,
  author    = {Westbrook, N. and Henkel, Carsten and Westbrook, C. I. and Landragin, A. and Labeyrie, G. and Cognet, L. and Savalli, V. and Horvath, G. and Aspect, Alain and Moelmer, Klaus and Courtois, J.-Y. and Phillips, W. D. and Kaiser, Rolf and Bagnato, V.},
  title     = {New physics with evanescent wave atomic mirrors : the van der Waals force and atomic diffraction},
  year      = {1998},
  abstract  = {After a brief introduction to the field of atom optics and to atomic mirrors, we present experimental results obtained in our group during the last two years while studying the reflection of rubidium atoms by an evanescent wave. These involve the first measurement of the van der Waals force between an atom in its ground state and a dielectric wall, as well as the demonstration of a reflection grating for atoms at normal incidence. We also consider the influence of quantum reflection and tunnelling phenomena. Further studies using the atomic mirror as a probe of the van der Waals interaction, and of very small surface roughness are briefly discussed.},
  language  = {en}
}
@article{ZhangHenkel2007,
  author    = {Zhang, Bo and Henkel, Carsten},
  title     = {Magnetic noise around metallic microstructures},
  issn      = {0021-8979},
  doi       = {10.1063/1.2800174},
  year      = {2007},
  abstract  = {We compute the local spectrum of the magnetic field near a metallic microstructure at finite temperature. Our main focus is on deviations from a plane-layered geometry for which we review the main properties. Arbitrary geometries are handled with the help of numerical calculations based on surface integral equations. The magnetic noise shows a significant polarization anisotropy above flat wires with finite lateral width, in stark contrast to an infinitely wide wire. Within the limits of a two-dimensional setting, our results provide accurate estimates for loss and dephasing rates in so-called `atom chip traps' based on metallic wires. A simple approximation based on the incoherent summation of local current elements gives qualitative agreement with the numerics, but fails to describe current correlations among neighboring objects.},
  language  = {en}
}
@article{GreffetHenkel2006,
  author    = {Greffet, Jean-Jacques and Henkel, Carsten},
  title     = {Rayonnement thermique coh{\´e}rent},
  issn      = {0290-0041},
  year      = {2006},
  abstract  = {Le rayonnement {\´e}lectromagn{\´e}tique produit par un corps {\`a} temp{\´e}rature T est g{\´e}n{\´e}ralement consid{\´e}r{\´e} comme l'exemple type du rayonnement incoh{\´e}rent que l'on oppose au rayonnement laser. L'un est quasi isotrope tandis que l'autre est tr{\`e}s directionnel, l'un a un large spectre tandis que l'autre est quasi-monochromatique. Aussi surprenant que cela puisse para{\^i}tre, le rayonnement thermique de bon nombre de corps est coh{\´e}rent lorsque l'on se place {\`a} une distance inf{\´e}rieure {\`a} la longueur d'onde de la surface {\´e}mettrice. Nous verrons que ces effets peuvent {\^e}tre pr{\´e}dits {\`a} l'aide d'une approche {\´e}lectromagn{\´e}tique du rayonnement thermique. Plusieurs exp{\´e}riences r{\´e}centes ont confirm{\´e} ces propri{\´e}t{\´e}s inattendues.},
  language  = {fr}
}
@article{IntravaiaHenkelLambrecht2007,
  author    = {Intravaia, Francesco and Henkel, Carsten and Lambrecht, Astrid},
  title     = {Role of surface plasmons in the Casimir effect},
  year      = {2007},
  abstract  = {In this paper we study the role of surface plasmon modes in the Casimir effect. The Casimir energy can be written as a sum over the modes of a real cavity and one may identify two sorts of modes, two evanescent surface plasmon modes and propagative modes. As one of the surface plasmon modes becomes propagative for some choice of parameters we adopt an adiabatic mode definition where we follow this mode into the propagative sector and count it together with the surface plasmon contribution, calling this contribution ``plasmonic''. We evaluate analytically the contribution of the plasmonic modes to the Casimir energy. Surprisingly we find that this becomes repulsive for intermediate and large mirror separations. The contribution of surface plasmons to the Casimir energy plays a fundamental role not only at short but also at large distances. This suggests possibilities to taylor the Casimir force via a manipulation of the surface plasmon properties.},
  language  = {en}
}
@article{GreffetHenkel2007,
  author    = {Greffet, Jean-Jacques and Henkel, Carsten},
  title     = {Coherent thermal radiation},
  issn      = {0010-7514},
  year      = {2007},
  abstract  = {The radiation emitted by a heated body is generally quoted as a typical example of incoherent radiation, in distinction to laser radiation. One is nearly isotropic, the other highly directional; one is spectrally broad, the other quasi-monochromatic. It may come as a surprise that the thermal radiation of a large number of substances is coherent, both in space and time, when it is observed at a distance from the body that is shorter than the wavelength. This behaviour can be understood within an electromagnetic approach to thermal emission. Several recent experiments have confirmed these unexpected properties.},
  language  = {en}
}
@article{Henkel2007,
  author    = {Henkel, Carsten},
  title     = {Laser theory in manifest Lindblad form},
  issn      = {0953-4075},
  year      = {2007},
  abstract  = {We discuss the laser theory for a single-mode laser with nonlinear gain. We focus in particular on a micromaser which is pumped with a dilute beam of excited atoms crossing the laser cavity. In the weak-coupling regime, an expansion in the coupling strength is developed that preserves the Lindblad form of the master equation, securing the positivity of the density matrix. This can be improved with an alternative approach, not restricted to weak coupling: the Lindblad operators are expanded in orthogonal polynomials adapted to the probability distribution for the atom-laser interaction time. Results for the photon statistics and the laser linewidth illustrate the theory.},
  language  = {en}
}
@article{IntravaiaHenkel2009,
  author    = {Intravaia, Francesco and Henkel, Carsten},
  title     = {Casimir interaction from magnetically coupled eddy currents},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.103.130405},
  year      = {2009},
  abstract  = {We study the quantum and thermal fluctuations of eddy (Foucault) currents in thick metallic plates. A Casimir interaction between two plates arises from the coupling via quasistatic magnetic fields. As a function of distance, the relevant eddy current modes cross over from a quantum to a thermal regime. These modes alone reproduce previously discussed thermal anomalies of the electromagnetic Casimir interaction between good conductors. In particular, they provide a physical picture for the Casimir entropy whose nonzero value at zero temperature arises from a correlated, glassy state.},
  language  = {en}
}
@article{BenAbdallahMessinaBiehsetal.2013,
  author    = {Ben-Abdallah, Philippe and Messina, Riccardo and Biehs, Svend-Age and Tschikin, Maria and Joulain, Karl and Henkel, Carsten},
  title     = {Heat superdiffusion in plasmonic nanostructure networks},
  series = {Physical review letters},
  volume    = {111},
  journal   = {Physical review letters},
  number    = {17},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {0031-9007},
  doi       = {10.1103/PhysRevLett.111.174301},
  pages     = {5},
  year      = {2013},
  abstract  = {The heat transport mediated by near-field interactions in networks of plasmonic nanostructures is shown to be analogous to a generalized random walk process. The existence of superdiffusive regimes is demonstrated both in linear ordered chains and in three-dimensional random networks by analyzing the asymptotic behavior of the corresponding probability distribution function. We show that the spread of heat in these networks is described by a type of Levy flight. The presence of such anomalous heat-transport regimes in plasmonic networks opens the way to the design of a new generation of composite materials able to transport heat faster than the normal diffusion process in solids.},
  language  = {en}
}
@article{BimonteHaakhHenkeletal.2010,
  author    = {Bimonte, Giuseppe and Haakh, Harald Richard and Henkel, Carsten and Intravaia, Francesco},
  title     = {Optical BCS conductivity at imaginary frequencies and dispersion energies of superconductors},
  issn      = {1751-8113},
  doi       = {10.1088/1751-8113/43/14/145304},
  year      = {2010},
  abstract  = {We present an efficient expression for the analytic continuation to arbitrary complex frequencies of the complex optical and ac conductivity of a homogeneous superconductor with an arbitrary mean free path. Knowledge of this quantity is fundamental in the calculation of thermodynamic potentials and dispersion energies involving type-I superconducting bodies. When considered for imaginary frequencies, our formula evaluates faster than previous schemes involving Kramers-Kronig transforms. A number of applications illustrate its efficiency: a simplified low-frequency expansion of the conductivity, the electromagnetic bulk self-energy due to longitudinal plasma oscillations, and the Casimir free energy of a superconducting cavity.},
  language  = {en}
}
@article{SchiefeleHenkel2009,
  author    = {Schiefele, J{\"u}rgen and Henkel, Carsten},
  title     = {Casimir energy of a BEC : from moderate interactions to the ideal gas},
  issn      = {1751-8113},
  doi       = {10.1088/1751-8113/42/4/045401},
  year      = {2009},
  abstract  = {Considering the Casimir effect due to phononic excitations of a weakly interacting dilute Bose-Einstein condensate ( BEC), we derive a renormalized expression for the zero-temperature Casimir energy E-C of a BEC confined to a parallel plate geometry with periodic boundary conditions. Our expression is formally equivalent to the free energy of a bosonic field at finite temperature, with a nontrivial density of modes that we compute analytically. As a function of the interaction strength, E-C smoothly describes the transition from the weakly interacting Bogoliubov regime to the non- interacting ideal BEC. For the weakly interacting case, E-C reduces to leading order to the Casimir energy due to zero- point fluctuations of massless phonon modes. In the limit of an ideal Bose gas, our result correctly describes the Casimir energy going to zero.},
  language  = {en}
}
@article{OstermeyerKornPuhlmannetal.2009,
  author    = {Ostermeyer, Martin and Korn, Dietmar and Puhlmann, Dirk and Henkel, Carsten and Eisert, Jens},
  title     = {Two-dimensional characterization of spatially entangled photon pairs},
  issn      = {0950-0340},
  doi       = {10.1080/09500340903359962},
  year      = {2009},
  abstract  = {We characterize the entanglement in position and momentum of photon pairs generated in type-II parametric down- conversion. Coincidence maps of the photon positions in the near-field and far-field planes are observed in two transverse dimensions using scanning fiber probes. We estimate the covariance matrix of an effective two-mode system and apply criteria for entanglement based on covariance matrices to certify space-momentum entanglement. The role of higher- order spatial modes for observing spatial entanglement between the two photons is discussed.},
  language  = {en}
}
@article{HaakhIntravaiaHenkel2010,
  author    = {Haakh, Harald Richard and Intravaia, Francesco and Henkel, Carsten},
  title     = {Temperature dependence of the plasmonic Casimir interaction},
  issn      = {1050-2947},
  doi       = {10.1103/Physreva.82.012507},
  year      = {2010},
  abstract  = {We investigate the role of surface plasmons in the electromagnetic Casimir effect at finite temperature, including situations out of global thermal equilibrium. The free energy is calculated analytically and expanded for different regimes of distances and temperatures. Similar to the zero-temperature case, the interaction changes from attraction to repulsion with distance. Thermal effects are shown to be negligible for small plate separations and at room temperature but become dominant and repulsive at large values of these parameters. In configurations out of global thermal equilibrium, we show that the selective excitation of surface plasmons can create a repulsive Casimir force between metal plates.},
  language  = {en}
}
@article{MkrtchianHenkel2020,
  author    = {Mkrtchian, Vanik E. and Henkel, Carsten},
  title     = {Green function solution of generalised boundary value problems},
  series = {Physics Letters A},
  volume    = {384},
  journal   = {Physics Letters A},
  number    = {23},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0375-9601},
  doi       = {10.1016/j.physleta.2020.126573},
  pages     = {5},
  year      = {2020},
  abstract  = {We construct an expression for the Green function of a differential operator satisfying nonlocal, homogeneous boundary conditions starting from the fundamental solution of the differential operator. This also provides the solution to the boundary value problem of an inhomogeneous partial differential equation with inhomogeneous, nonlocal boundary conditions. The construction applies for a broad class of linear partial differential equations and linear boundary conditions.},
  language  = {en}
}
@article{CockburnNegrettiProukakisetal.2011,
  author    = {Cockburn, S. P. and Negretti, Antonio and Proukakis, N. P. and Henkel, Carsten},
  title     = {Comparison between microscopic methods for finite-temperature Bose gases},
  series = {Physical review : A, Atomic, molecular, and optical physics},
  volume    = {83},
  journal   = {Physical review : A, Atomic, molecular, and optical physics},
  number    = {4},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1050-2947},
  doi       = {10.1103/PhysRevA.83.043619},
  pages     = {29},
  year      = {2011},
  abstract  = {We analyze the equilibrium properties of a weakly interacting, trapped quasi-one-dimensional Bose gas at finite temperatures and compare different theoretical approaches. We focus in particular on two stochastic theories: a number-conserving Bogoliubov (NCB) approach and a stochastic Gross-Pitaevskii equation (SGPE) that have been extensively used in numerical simulations. Equilibrium properties like density profiles, correlation functions, and the condensate statistics are compared to predictions based upon a number of alternative theories. We find that due to thermal phase fluctuations, and the corresponding condensate depletion, the NCB approach loses its validity at relatively low temperatures. This can be attributed to the change in the Bogoliubov spectrum, as the condensate gets thermally depleted, and to large fluctuations beyond perturbation theory. Although the two stochastic theories are built on different thermodynamic ensembles (NCB, canonical; SGPE, grand-canonical), they yield the correct condensate statistics in a large Bose-Einstein condensate (BEC) (strong enough particle interactions). For smaller systems, the SGPE results are prone to anomalously large number fluctuations, well known for the grand-canonical, ideal Bose gas. Based on the comparison of the above theories to the modified Popov approach, we propose a simple procedure for approximately extracting the Penrose-Onsager condensate from first-and second-order correlation functions that is both computationally convenient and of potential use to experimentalists. This also clarifies the link between condensate and quasicondensate in the Popov theory of low-dimensional systems.},
  language  = {en}
}
@article{IntravaiaBehuninHenkeletal.2016,
  author    = {Intravaia, F. and Behunin, R. O. and Henkel, Carsten and Busch, K. and Dalvit, D. A. R.},
  title     = {Failure of Local Thermal Equilibrium in Quantum Friction},
  series = {Physical review letters},
  volume    = {117},
  journal   = {Physical review letters},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {0031-9007},
  doi       = {10.1103/PhysRevLett.117.100402},
  pages     = {989 -- 1010},
  year      = {2016},
  abstract  = {Recent progress in manipulating atomic and condensed matter systems has instigated a surge of interest in nonequilibrium physics, including many-body dynamics of trapped ultracold atoms and ions, near-field radiative heat transfer, and quantum friction. Under most circumstances the complexity of such nonequilibrium systems requires a number of approximations to make theoretical descriptions tractable. In particular, it is often assumed that spatially separated components of a system thermalize with their immediate surroundings, although the global state of the system is out of equilibrium. This powerful assumption reduces the complexity of nonequilibrium systems to the local application of well-founded equilibrium concepts. While this technique appears to be consistent for the description of some phenomena, we show that it fails for quantum friction by underestimating by approximately 80\% the magnitude of the drag force. Our results show that the correlations among the components of driven, but steady-state, quantum systems invalidate the assumption of local thermal equilibrium, calling for a critical reexamination of this approach for describing the physics of nonequilibrium systems.},
  language  = {en}
}
@article{IntravaiaBehuninHenkeletal.2016,
  author    = {Intravaia, F. and Behunin, R. O. and Henkel, Carsten and Busch, K. and Dalvit, D. A. R.},
  title     = {Non-Markovianity in atom-surface dispersion forces},
  series = {Physical review : A, Atomic, molecular, and optical physics},
  volume    = {94},
  journal   = {Physical review : A, Atomic, molecular, and optical physics},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2469-9926},
  doi       = {10.1103/PhysRevA.94.042114},
  pages     = {16},
  year      = {2016},
  abstract  = {We discuss the failure of the Markov approximation in the description of atom-surface fluctuation-induced interactions, both in equilibrium (Casimir-Polder forces) and out of equilibrium (quantum friction). Using general theoretical arguments, we show that the Markov approximation can lead to erroneous predictions of such phenomena with regard to both strength and functional dependencies on system parameters. In particular, we show that the long-time power-law tails of two-time dipole correlations and their corresponding low-frequency behavior, neglected in the Markovian limit, affect the prediction of the force. Our findings highlight the importance of non-Markovian effects in dispersion interactions.},
  language  = {en}
}
@article{HaakhHenkelSpagnoloetal.2014,
  author    = {Haakh, Harald R. and Henkel, Carsten and Spagnolo, Salvatore and Rizzuto, Lucia and Passante, Roberto},
  title     = {Dynamical Casimir-Polder interaction between an atom and surface plasmons},
  series = {Physical review : A, Atomic, molecular, and optical physics},
  volume    = {89},
  journal   = {Physical review : A, Atomic, molecular, and optical physics},
  number    = {2},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1050-2947},
  doi       = {10.1103/PhysRevA.89.022509},
  pages     = {11},
  year      = {2014},
  abstract  = {We investigate the time-dependent Casimir-Polder potential of a polarizable two-level atom placed near a surface of arbitrary material, after a sudden change in the parameters of the system. Different initial conditions are taken into account. For an initially bare ground-state atom, the time-dependent Casimir-Polder energy reveals how the atom is "being dressed" by virtual, matter-assisted photons. We also study the transient behavior of the Casimir-Polder interaction between the atom and the surface starting from a partially dressed state, after an externally induced change in the atomic level structure or transition dipoles. The Heisenberg equations are solved through an iterative technique for both atomic and field operators in the medium-assisted electromagnetic field quantization scheme. We analyze, in particular, how the time evolution of the interaction energy depends on the optical properties of the surface, in particular on the dispersion relation of surface plasmon polaritons. The physical significance and the limits of validity of the obtained results are discussed in detail.},
  language  = {en}
}
@article{IntravaiaMkrtchianBuhmannetal.2015,
  author    = {Intravaia, Francesco and Mkrtchian, Vanik E. and Buhmann, Stefan Yoshi and Scheel, Stefan and Dalvit, Diego A. R. and Henkel, Carsten},
  title     = {Friction forces on atoms after acceleration},
  series = {Journal of physics : Condensed matter},
  volume    = {27},
  journal   = {Journal of physics : Condensed matter},
  number    = {21},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0953-8984},
  doi       = {10.1088/0953-8984/27/21/214020},
  pages     = {19},
  year      = {2015},
  abstract  = {The aim of this paper is to revisit the calculation of atom-surface quantum friction in the quantum field theory formulation put forward by Barton (2010 New J. Phys. 12 113045). We show that the power dissipated into field excitations and the associated friction force depend on how the atom is boosted from being initially at rest to a configuration in which it is moving at constant velocity (nu) parallel to the planar interface. In addition, we point out that there is a subtle cancellation between the one-photon and part of the two-photon dissipating power, resulting in a leading order contribution to the frictional power which goes as nu(4). These results are also confirmed by an alternative calculation of the average radiation force, which scales as nu(3).},
  language  = {en}
}
@article{PieplowHenkel2015,
  author    = {Pieplow, Gregor and Henkel, Carsten},
  title     = {Cherenkov friction on a neutral particle moving parallel to a dielectric},
  series = {Journal of physics : Condensed matter},
  volume    = {27},
  journal   = {Journal of physics : Condensed matter},
  number    = {21},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0953-8984},
  doi       = {10.1088/0953-8984/27/21/214001},
  pages     = {7},
  year      = {2015},
  abstract  = {We describe a simple mechanism of quantum friction for a particle moving parallel to a dielectric, based on a fully relativistic framework and the assumption of local equilibrium. The Cherenkov effect explains how the bare ground state becomes globally unstable and how fluctuations of the electromagnetic field and the particle's dipole are converted into pairs of excitations. Modeling the particle as a silver nano-sphere, we investigate the spectrum of the force and its velocity dependence. We find that the damping of the plasmon resonance in the silver particle has a relatively strong impact near the Cherenkov threshold velocity. We also present an expansion of the friction force near the threshold velocity for both damped and undamped particles.},
  language  = {en}
}
@article{DialloHenkel2015,
  author    = {Diallo, Abdoulaye and Henkel, Carsten},
  title     = {Excitations at the border of a condensate},
  series = {Journal of physics : B, Atomic, molecular and optical physics},
  volume    = {48},
  journal   = {Journal of physics : B, Atomic, molecular and optical physics},
  number    = {16},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0953-4075},
  doi       = {10.1088/0953-4075/48/16/165302},
  pages     = {14},
  year      = {2015},
  abstract  = {We solve the Bogoliubov equations for an inhomogeneous condensate in the vicinity of a linear turning point. A stable integration scheme is developed using a transformation into an adiabatic basis. We identify boundary modes trapped in a potential whose shape is similar to a Hartree-Fock mean-field treatment. These modes are non-resonantly excited when bulk modes reflect at the turning point and contribute significantly to the spectrum of local density fluctuations.},
  language  = {en}
}
@article{MkrtchianHenkel2014,
  author    = {Mkrtchian, Vanik E. and Henkel, Carsten},
  title     = {On non-equilibrium photon distributions in the Casimir effect},
  series = {Annalen der Physik},
  volume    = {526},
  journal   = {Annalen der Physik},
  number    = {1-2},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0003-3804},
  doi       = {10.1002/andp.201300135},
  pages     = {87 -- 101},
  year      = {2014},
  abstract  = {The electromagnetic field in a typical geometry of the Casimir effect is described in the Schwinger-Keldysh formalism. The main result is the photon distribution function (Keldysh Green function) in any stationary state of the field. A two-plate geometry with a sliding interface in local equilibrium is studied in detail, and full agreement with the results of Rytov fluctuation electrodynamics is found.},
  language  = {en}
}
@article{ZuritaSanchezHenkel2012,
  author    = {Zurita-Sanchez, Jorge R. and Henkel, Carsten},
  title     = {Acoustic waves from mechanical impulses due to fluorescence resonant energy (Forster) transfer Blowing a whistle with light},
  series = {epl : a letters journal exploring the frontiers of physics},
  volume    = {97},
  journal   = {epl : a letters journal exploring the frontiers of physics},
  number    = {4},
  publisher = {EDP Sciences},
  address   = {Mulhouse},
  issn      = {0295-5075},
  doi       = {10.1209/0295-5075/97/43002},
  pages     = {6},
  year      = {2012},
  abstract  = {We present a momentum transfer mechanism mediated by electromagnetic fields that originates in a system of two nearby molecules: one excited (donor D*) and the other in ground state (acceptor A). An intermolecular force related to fluorescence resonant energy or Forster transfer (FRET) arises in the unstable D* A molecular system, which differs from the equilibrium van der Waals interaction. Due to the its finite lifetime, a mechanical impulse is imparted to the relative motion in the system. We analyze the FRET impulse when the molecules are embedded in free space and find that its magnitude can be much greater than the single recoil photon momentum, getting comparable with the thermal momentum (Maxwell-Boltzmann distribution) at room temperature. In addition, we propose that this FRET impulse can be exploited in the generation of acoustic waves inside a film containing layers of donor and acceptor molecules, when a picosecond laser pulse excites the donors. This acoustic transient is distinguishable from that produced by thermal stress due to laser absorption, and may therefore play a role in photoacoustic spectroscopy. The effect can be seen as exciting a vibrating system like a string or organ pipe with light; it may be used as an opto-mechanical transducer.},
  language  = {en}
}
@article{HaakhHenkel2012,
  author    = {Haakh, Harald Richard and Henkel, Carsten},
  title     = {Magnetic near fields as a probe of charge transport in spatially dispersive conductors},
  series = {The European physical journal : B, Condensed matter and complex systems},
  volume    = {85},
  journal   = {The European physical journal : B, Condensed matter and complex systems},
  number    = {1},
  publisher = {Springer},
  address   = {New York},
  issn      = {1434-6028},
  doi       = {10.1140/epjb/e2011-20567-1},
  pages     = {12},
  year      = {2012},
  abstract  = {We calculate magnetic field fluctuations above a conductor with a nonlocal response (spatial dispersion) and consider a large range of distances. The cross-over from ballistic to diffusive charge transport leads to a reduced noise spectrum at distances below the electronic mean free path, as compared to a local description. We also find that the mean free path provides a lower limit to the correlation (coherence) length of the near field fluctuations. The short-distance behaviour is common to a wide range of materials, including semiconductors and superconductors. Our discussion is aimed at atom chip experiments where spin-flip transitions give access to material properties with mesoscopic spatial resolution. The results also hint at fundamental limits to the coherent operation of miniaturised atom traps and matter-wave interferometers.},
  language  = {en}
}
@article{MuellerHaakhCalarcoetal.2011,
  author    = {M{\"u}ller, Matthias M. and Haakh, Harald R. and Calarco, Tommaso and Koch, Christiane P. and Henkel, Carsten},
  title     = {Prospects for fast Rydberg gates on an atom chip},
  series = {Quantum information processing},
  volume    = {10},
  journal   = {Quantum information processing},
  number    = {6},
  publisher = {Springer},
  address   = {New York},
  issn      = {1570-0755},
  doi       = {10.1007/s11128-011-0296-0},
  pages     = {771 -- 792},
  year      = {2011},
  abstract  = {Atom chips are a promising candidate for a scalable architecture for quantum information processing provided a universal set of gates can be implemented with high fidelity. The difficult part in achieving universality is the entangling two-qubit gate. We consider a Rydberg phase gate for two atoms trapped on a chip and employ optimal control theory to find the shortest gate that still yields a reasonable gate error. Our parameters correspond to a situation where the Rydberg blockade regime is not yet reached. We discuss the role of spontaneous emission and the effect of noise from the chip surface on the atoms in the Rydberg state.},
  language  = {en}
}
@article{SchiefeleHenkel2011,
  author    = {Schiefele, Juergen and Henkel, Carsten},
  title     = {Bosonic enhancement of spontaneous emission near an interface},
  series = {Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics},
  volume    = {375},
  journal   = {Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics},
  number    = {3},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0375-9601},
  doi       = {10.1016/j.physleta.2010.11.058},
  pages     = {680 -- 684},
  year      = {2011},
  abstract  = {We show how the spontaneous emission rate of an excited two-level atom placed in a trapped Bose-Einstein condensate of ground-state atoms is enhanced by bosonic stimulation. This stimulation depends on the overlap of the excited matter-wave packet with the macroscopically occupied condensate wave function, and provides a probe of the spatial coherence of the Bose gas. The effect can be used to amplify the distance-dependent decay rate of an excited atom near an interface.},
  language  = {en}
}
@article{JoulainBenAbdallahChapuisetal.2014,
  author    = {Joulain, Karl and Ben-Abdallah, Philippe and Chapuis, Pierre-Olivier and De Wilde, Y. and Babuty, A. and Henkel, Carsten},
  title     = {Strong tip-sample coupling in thermal radiation scanning tunneling microscopy},
  series = {Journal of quantitative spectroscopy \& radiative transfer},
  volume    = {136},
  journal   = {Journal of quantitative spectroscopy \& radiative transfer},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0022-4073},
  doi       = {10.1016/j.jqsrt.2013.12.006},
  pages     = {1 -- 15},
  year      = {2014},
  language  = {en}
}
@article{PieplowHenkel2013,
  author    = {Pieplow, Gregor and Henkel, Carsten},
  title     = {Fully covariant radiation force on a polarizable particle},
  series = {New journal of physics : the open-access journal for physics},
  volume    = {15},
  journal   = {New journal of physics : the open-access journal for physics},
  number    = {4},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/15/2/023027},
  pages     = {17},
  year      = {2013},
  abstract  = {The electromagnetic force on a polarizable particle is calculated in a covariant framework. Local equilibrium temperatures for the electromagnetic field and the particle's dipole moment are assumed, using a relativistic formulation of the fluctuation-dissipation theorem. Two examples illustrate radiative friction forces: a particle moving through a homogeneous radiation background and above a planar interface. Previous results for arbitrary relative velocities are recovered in a compact way.},
  language  = {en}
}
@article{BoedeckerHenkel2012,
  author    = {B{\"o}decker, Geesche and Henkel, Carsten},
  title     = {Validity of the quantum regression theorem for resonance fluorescence in a photonic crystal},
  series = {Annalen der Physik},
  volume    = {524},
  journal   = {Annalen der Physik},
  number    = {12},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0003-3804},
  doi       = {10.1002/andp.201200135},
  pages     = {805 -- 813},
  year      = {2012},
  abstract  = {Correlation functions of a driven two-level system embedded in a photonic crystal are analyzed. The spectral density of the photonic bands near a gap makes this system non-Markovian. The equations of motion for two-time correlations are derived by two different methods, the quantum regression theorem and the fluctuation dissipation theorem, and found to be the same.},
  language  = {en}
}
@article{HenkelIntravaia2010,
  author    = {Henkel, Carsten and Intravaia, Francesco},
  title     = {On the Casimir entropy between "perfect crystals"},
  issn      = {0217-751X},
  doi       = {10.1142/S0217751x10049608},
  year      = {2010},
  abstract  = {We give a re-interpretation of an 'entropy defect' in the electromagnetic Casimir effect. The electron gas in a perfect crystal is an electromagnetically disordered system whose entropy contains a finite Casimir- like contribution. The Nernst theorem (third law of thermodynamics) is not applicable.},
  language  = {en}
}
@article{JaphaZhouKeiletal.2016,
  author    = {Japha, Yonathan and Zhou, Shuyu and Keil, Mark and Folman, Ron and Henkel, Carsten and Vardi, Amichay},
  title     = {Suppression and enhancement of decoherence in an atomic Josephson junction},
  series = {NEW JOURNAL OF PHYSICS},
  volume    = {18},
  journal   = {NEW JOURNAL OF PHYSICS},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/18/5/055008},
  pages     = {22},
  year      = {2016},
  abstract  = {We investigate the role of interatomic interactions when a Bose gas, in a double-well potential with a finite tunneling probability (a 'Bose-Josephson junction'), is exposed to external noise. We examine the rate of decoherence of a system initially in its ground state with equal probability amplitudes in both sites. The noise may induce two kinds of effects: firstly, random shifts in the relative phase or number difference between the two wells and secondly, loss of atoms from the trap. The effects of induced phase fluctuations are mitigated by atom-atom interactions and tunneling, such that the dephasing rate may be suppressed by half its single-atom value. Random fluctuations may also be induced in the population difference between the wells, in which case atom-atom interactions considerably enhance the decoherence rate. A similar scenario is predicted for the case of atom loss, even if the loss rates from the two sites are equal. We find that if the initial state is number-squeezed due to interactions, then the loss process induces population fluctuations that reduce the coherence across the junction. We examine the parameters relevant for these effects in a typical atom chip device, using a simple model of the trapping potential, experimental data, and the theory of magnetic field fluctuations near metallic conductors. These results provide a framework for mapping the dynamical range of barriers engineered for specific applications and set the stage for more complex atom circuits ('atomtronics').},
  language  = {en}
}
@article{KumphHenkelRabletal.2016,
  author    = {Kumph, Muir and Henkel, Carsten and Rabl, Peter and Brownnutt, Michael and Blatt, Rainer},
  title     = {Electric-field noise above a thin dielectric layer on metal electrodes},
  series = {NEW JOURNAL OF PHYSICS},
  volume    = {18},
  journal   = {NEW JOURNAL OF PHYSICS},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/18/2/023020},
  pages     = {1125 -- 1136},
  year      = {2016},
  abstract  = {The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare metal. Close to this layered surface, the power spectral density of the electric field varies with the inverse fourth power of the distance to the surface, rather than with the inverse square, as it would above a bare metal surface. Furthermore, compared to a clean metal, where the noise spectrum does not vary with frequency (in the radio-wave and microwave bands), the dielectric layer can generate electricfield noise which scales in inverse proportion to the frequency. For various realistic scenarios, the noise levels predicted from this model are comparable to those observed in trapped-ion experiments. Thus, these findings are of particular importance for the understanding and mitigation of unwanted heating and decoherence in miniaturized ion traps.},
  language  = {en}
}
@article{HenkelSauerProukakis2017,
  author    = {Henkel, Carsten and Sauer, Tim-O and Proukakis, N. P.},
  title     = {Cross-over to quasi-condensation: mean-field theories and beyond},
  series = {Journal of physics : B, Atomic, molecular and optical physics},
  volume    = {50},
  journal   = {Journal of physics : B, Atomic, molecular and optical physics},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0953-4075},
  doi       = {10.1088/1361-6455/aa6888},
  pages     = {19},
  year      = {2017},
  abstract  = {We analyze the cross-over of a homogeneous, weakly interacting Bose gas in one dimension from the ideal gas into the dense quasi-condensate phase. We review a number of mean-field theories, perturbative or self-consistent, and provide accurate evaluations of equation of state, density fluctuations, and correlation functions. A smooth crossover is reproduced by classical-field simulations based on the stochastic Gross-Pitaevskii equation and the Yang-Yang solution to the one-dimensional Bose gas.},
  language  = {en}
}
@article{JoulainHenkelGreffet2006,
  author    = {Joulain, Karl and Henkel, Carsten and Greffet, Jean-Jacques},
  title     = {Influence of the dependence in temperature of the optical properties of materials on the Casimir force},
  series = {Journal de physique IV},
  volume    = {135},
  journal   = {Journal de physique IV},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  issn      = {1155-4339},
  doi       = {10.1051/jp4:2006135021},
  pages     = {113 -- 114},
  year      = {2006},
  abstract  = {Nous {\´e}valuons la force de Casimir entre deux surfaces planes m{\´e}talliques constitu{\´e}es d'argent. Nous prenons, pour effectuer cette {\´e}valuation, des propri{\´e}t{\´e}s optiques de l'argent {\`a} diff{\´e}rentes temp{\´e}ratures [1]. Nous montrons que cette d{\´e}pendance en temp{\´e}rature modifie la force de Casimir (de 0.2\%) y compris {\`a} des distances inf{\´e}rieures {\`a} la longueur d'onde thermique.},
  language  = {fr}
}
@article{PerrinColombeMercieretal.2006,
  author    = {Perrin, Helene and Colombe, Yves and Mercier, Brigitte and Lorent, Vincent and Henkel, Carsten},
  title     = {Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror},
  series = {Journal of physics : B, Atomic, molecular and optical physics},
  volume    = {39},
  journal   = {Journal of physics : B, Atomic, molecular and optical physics},
  publisher = {IOP Publ.},
  address   = {Bristol},
  issn      = {0953-4075},
  doi       = {10.1088/0953-4075/39/22/009},
  pages     = {4649 -- 4658},
  year      = {2006},
  abstract  = {We present experimental results showing the diffuse reflection of a Bose Einstein condensate from a rough mirror, consisting of a dielectric substrate supporting a blue-detuned evanescent wave. The scattering is anisotropic, more pronounced in the direction of the surface propagation of the evanescent wave. These results agree very well with theoretical predictions.},
  language  = {en}
}
@misc{BouchouleSchemmerHenkel2018,
  author    = {Bouchoule, Isabelle and Schemmer, Max and Henkel, Carsten},
  title     = {Cooling phonon modes of a Bose condensate with uniform few body losses},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1029},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-46881},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-468811},
  pages     = {20},
  year      = {2018},
  abstract  = {We present a general analysis of the cooling produced by losses on condensates or quasi-condensates. We study how the occupations of the collective phonon modes evolve in time, assuming that the loss process is slow enough so that each mode adiabatically follows the decrease of the mean density. The theory is valid for any loss process whose rate is proportional to the jth power of the density, but otherwise spatially uniform. We cover both homogeneous gases and systems confined in a smooth potential. For a low-dimensional gas, we can take into account the modified equation of state due to the broadening of the cloud width along the tightly confined directions, which occurs for large interactions. We find that at large times, the temperature decreases proportionally to the energy scale mc2, where m is the mass of the particles and c the sound velocity. We compute the asymptotic ratio of these two quantities for different limiting cases: a homogeneous gas in any dimension and a one-dimensional gas in a harmonic trap.},
  language  = {en}
}
@article{HenkelKlimchitskayaMostepanenko2018,
  author    = {Henkel, Carsten and Klimchitskaya, G. L. and Mostepanenko, V. M.},
  title     = {Influence of the chemical potential on the Casimir-Polder interaction between an atom and gapped graphene or a graphene-coated substrate},
  series = {Physical review : A, Atomic, molecular, and optical physics},
  volume    = {97},
  journal   = {Physical review : A, Atomic, molecular, and optical physics},
  number    = {3},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2469-9926},
  doi       = {10.1103/PhysRevA.97.032504},
  pages     = {12},
  year      = {2018},
  abstract  = {We present a formalism based on first principles of quantum electrodynamics at nonzero temperature which permits us to calculate the Casimir-Polder interaction between an atom and a graphene sheet with arbitrary mass gap and chemical potential, including graphene-coated substrates. The free energy and force of the Casimir-Polder interaction are expressed via the polarization tensor of graphene in (2 + 1)-dimensional space-time in the framework of the Dirac model. The obtained expressions are used to investigate the influence of the chemical potential of graphene on the Casimir-Polder interaction. Computations are performed for an atom of metastable helium interacting with either a freestanding graphene sheet or a graphene-coated substrate made of amorphous silica. It is shown that the impacts of the nonzero chemical potential and the mass gap on the Casimir-Polder interaction are in opposite directions, by increasing and decreasing the magnitudes of the free energy and force, respectively. It turns out, however, that the temperature-dependent part of the Casimir-Polder interaction is decreased by a nonzero chemical potential, whereas the mass gap increases it compared to the case of undoped, gapless graphene. The physical explanation for these effects is provided. Numerical computations of the Casimir-Polder interaction are performed at various temperatures and atom-graphene separations.},
  language  = {en}
}
@article{BouchouleSchemmerHenkel2018,
  author    = {Bouchoule, Isabelle and Schemmer, Max and Henkel, Carsten},
  title     = {Cooling phonon modes of a Bose condensate with uniform few body losses},
  series = {Scipost Physics},
  volume    = {5},
  journal   = {Scipost Physics},
  number    = {5},
  publisher = {Scipost foundation},
  address   = {Amsterdam},
  issn      = {2542-4653},
  doi       = {10.21468/SciPostPhys.5.5.043},
  pages     = {18},
  year      = {2018},
  abstract  = {We present a general analysis of the cooling produced by losses on condensates or quasi-condensates. We study how the occupations of the collective phonon modes evolve in time, assuming that the loss process is slow enough so that each mode adiabatically follows the decrease of the mean density. The theory is valid for any loss process whose rate is proportional to the jth power of the density, but otherwise spatially uniform. We cover both homogeneous gases and systems confined in a smooth potential. For a low-dimensional gas, we can take into account the modified equation of state due to the broadening of the cloud width along the tightly confined directions, which occurs for large interactions. We find that at large times, the temperature decreases proportionally to the energy scale mc(2), where m is the mass of the particles and c the sound velocity. We compute the asymptotic ratio of these two quantities for different limiting cases: a homogeneous gas in any dimension and a one-dimensional gas in a harmonic trap.},
  language  = {en}
}
@article{HenkelJacobStoppetal.2019,
  author    = {Henkel, Carsten and Jacob, Georg and Stopp, Felix and Schmidt-Kaler, Ferdinand and Keil, Mark and Japha, Yonathan and Folman, Ron},
  title     = {Stern-Gerlach splitting of low-energy ion beams},
  series = {New journal of physics : the open-access journal for physics},
  volume    = {21},
  journal   = {New journal of physics : the open-access journal for physics},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/ab36c7},
  pages     = {14},
  year      = {2019},
  abstract  = {We present a feasibility study with several magnetic field configurations for creating spin-dependent forces that can split a low-energy ion beam by the Stern-Gerlach (SG) effect. To the best of our knowledge, coherent spin-splittings of charged particles have yet to be realised. Our proposal is based on ion source parameters taken from a recent experiment that demonstrated single-ion implantation from a high-brightness ion source combined with a radio-frequency Paul trap. The inhomogeneous magnetic fields can be created by permanently magnetised microstructures or from current-carrying wires with sizes in the micron range, such as those recently used in a successful implementation of the SG effect with neutral atoms. All relevant forces (Lorentz force and image charges) are taken into account, and measurable splittings are found by analytical and numerical calculations.},
  language  = {en}
}
@article{HenkelSchmidt2019,
  author    = {Henkel, Carsten and Schmidt, Paul Philip},
  title     = {On anomalously large nano-scale heat transfer between metals},
  series = {Journal of the Optical Society of America : B, Optical physics},
  volume    = {36},
  journal   = {Journal of the Optical Society of America : B, Optical physics},
  number    = {4},
  publisher = {Optical Society of America},
  address   = {Washington},
  issn      = {0740-3224},
  doi       = {10.1364/JOSAB.36.000C10},
  pages     = {C10 -- C14},
  year      = {2019},
  abstract  = {Non-contact heat transfer between two bodies is more efficient than the Stefan-Boltzmann law when the distances are on the nanometer scale (shorter than Wien's wavelength), due to contributions of thermally excited near fields. This is usually described in terms of the fluctuation electrodynamics due to Rytov, Levin, and co-workers. Recent experiments in the tip-plane geometry have reported "giant" heat currents between metallic (gold) objects, exceeding even the expectations of Rytov theory. We discuss a simple model that describes the distance dependence of the data and permits us to compare to a plate-plate geometry, as in the proximity (or Derjaguin) approximation. We extract an area density of active channels which is of the same order for the experiments performed by the groups of Kittel (Oldenburg) and Reddy (Ann Arbor). It is argued that mechanisms that couple phonons to an oscillating surface polarization are likely to play a role.},
  language  = {en}
}
@article{Henkel2021,
  author    = {Henkel, Carsten},
  title     = {Heat transfer and entanglement},
  series = {Annalen der Physik},
  volume    = {533},
  journal   = {Annalen der Physik},
  number    = {10},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0003-3804},
  doi       = {10.1002/andp.202100089},
  pages     = {15},
  year      = {2021},
  abstract  = {The non-equilibrium state of two oscillators with a mutual interaction and coupled to separate heat baths is discussed. Bosonic baths are considered, and an exact spectral representation for the elements of the covariance matrix is provided analytically. A wide class of spectral densities for the relevant bath modes is allowed for. The validity of the fluctuation-dissipation relation is established for global equilibrium (both baths at the same temperature) in the stationary state. Spectral measures of entanglement are suggested by comparing to the equilibrium spectrum of zero-point fluctuations. No rotating-wave approximation is applied, and anomalous heat transport from cold to hot bath, as reported in earlier work, is demonstrated not to occur.},
  language  = {en}
}
@article{Henkel2020,
  author    = {Henkel, Carsten},
  title     = {Thermally excited quasiparticles in metals, dispersion forces, and the thermal anomaly},
  series = {Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics},
  volume    = {35},
  journal   = {Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics},
  number    = {3},
  publisher = {World Scientific},
  address   = {Singapore},
  issn      = {0217-7323},
  doi       = {10.1142/S021773232040009X},
  pages     = {9},
  year      = {2020},
  abstract  = {We provide a brief review of the contribution of thermally excited carriers to dispersion forces. In a metal, these carriers generate charge and current fluctuations whose spectral frequencies are comparable to k(B)T/(h) over bar. They are very likely responsible for the "plasma vs. Drude" anomaly.},
  language  = {en}
}
@article{Henkel2017,
  author    = {Henkel, Carsten},
  title     = {Nanoscale Thermal Transfer},
  series = {Zeitschrift f{\"u}r Naturforschung A},
  volume    = {72},
  journal   = {Zeitschrift f{\"u}r Naturforschung A},
  number    = {2},
  publisher = {De Gruyter},
  address   = {Berlin},
  issn      = {0932-0784},
  doi       = {10.1515/zna-2016-0372},
  pages     = {99 -- 108},
  year      = {2017},
  abstract  = {An electromagnetic theory of thermal radiation is outlined, based on the fluctuation electrodynamics of Rytov and co-workers. We discuss the basic concepts and the status of different approximations. The physical content is illustrated with a few examples on near-field heat transfer.},
  language  = {en}
}
@article{NematiHenkelAnders2022,
  author    = {Nemati, Somayyeh and Henkel, Carsten and Anders, Janet},
  title     = {Coupling function from bath density of states},
  series = {epl : a letters journal exploring the frontiers of physics},
  volume    = {139},
  journal   = {epl : a letters journal exploring the frontiers of physics},
  number    = {3},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0295-5075},
  doi       = {10.1209/0295-5075/ac7b42},
  pages     = {7},
  year      = {2022},
  abstract  = {Modelling of an open quantum system requires knowledge of parameters that specify how it couples to its environment. However, beyond relaxation rates, realistic parameters for specific environments and materials are rarely known. Here we present a method of inferring the coupling between a generic system and its bosonic (e.g., phononic) environment from the experimentally measurable density of states (DOS). With it we confirm that the DOS of the well-known Debye model for three-dimensional solids is physically equivalent to choosing an Ohmic bath. We further match a real phonon DOS to a series of Lorentzian coupling functions, allowing us to determine coupling parameters for gold, yttrium iron garnet (YIG) and iron as examples. The results illustrate how to obtain material-specific dynamical properties, such as memory kernels. The proposed method opens the door to more accurate modelling of relaxation dynamics, for example for phonon-dominated spin damping in magnetic materials.},
  language  = {en}
}
@article{HorovitzHenkel2021,
  author    = {Horovitz, Baruch and Henkel, Carsten},
  title     = {Spin entanglement via scanning tunneling microscope current},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {104},
  journal   = {Physical review : B, Condensed matter and materials physics},
  number    = {8},
  publisher = {American Physical Society},
  address   = {Ridge, NY},
  issn      = {2469-9950},
  doi       = {10.1103/PhysRevB.104.L081405},
  pages     = {5},
  year      = {2021},
  abstract  = {We consider a system of two spins under a scanning tunneling microscope bias and derive its master equation. We find that the tunneling elements to the electronic contacts (tip and substrate) generate an exchange interaction between the spins as well as a Dzyaloshinskii-Moriya interaction in the presence of spin-orbit coupling. The tunnel current spectrum then shows additional lines compared to conventional spin-resonance experiments. When the spins have degenerate Larmor frequencies and equal tunneling amplitudes (without spin orbit), there is a dark state with a vanishing decay rate. The coupling to the electronic environment generates significant spin-spin entanglement via the dark state, even if the initial state is nonentangled.},
  language  = {en}
}
@article{EiznerHorovitzHenkel2012,
  author    = {Eizner, E. and Horovitz, Baruch and Henkel, Carsten},
  title     = {Van der waals-casimir-polder interaction of an atom with a composite surface},
  series = {The European physical journal : D, Atomic, molecular, optical and plasma physics},
  volume    = {66},
  journal   = {The European physical journal : D, Atomic, molecular, optical and plasma physics},
  number    = {12},
  publisher = {Springer},
  address   = {New York},
  issn      = {1434-6060},
  doi       = {10.1140/epjd/e2012-30294-x},
  pages     = {11},
  year      = {2012},
  abstract  = {We study the dispersion interaction of the van der Waals and Casimir-Polder (vdW-CP) type between a neutral atom and the surface of a conductor by allowing for nonlocal electrodynamics, i.e. electron diffusion. We consider two models: (i) bulk diffusion, and (ii) diffusion in a surface charge layer. In both cases, we find that the transition to a semiconductor as a function of the conductivity is continuous, unlike the case of a local model. The relevant parameter is the electric screening length and depends on the carrier diffusion constant. We find that for distances comparable to the screening length, vdW-CP data can distinguish between bulk and surface diffusion, hence it can be a sensitive probe for surface states.},
  language  = {en}
}
@article{HorovitzHenkel2012,
  author    = {Horovitz, Baruch and Henkel, Carsten},
  title     = {Surface plasmons at composite surfaces with diffusive charges},
  series = {epl : a letters journal exploring the frontiers of physics},
  volume    = {97},
  journal   = {epl : a letters journal exploring the frontiers of physics},
  number    = {5},
  publisher = {EDP Sciences},
  address   = {Mulhouse},
  issn      = {0295-5075},
  doi       = {10.1209/0295-5075/97/57010},
  pages     = {6},
  year      = {2012},
  abstract  = {Metal surfaces with disorder or with nanostructure modifications are studied, allowing for a localized charge layer (CL) in addition to continuous charges (CC) in the bulk, both charges having a compressional or diffusive nonlocal response. The notorious problem of "additional boundary conditions" is resolved with the help of a Boltzmann equation that involves the scattering between the two charge types. Depending on the strength of this scattering, the oscillating charges can be dominantly CC or CL; the surface plasmon (SP) resonance acquires then a relatively small linewidth, in agreement with a large set of data. With a few parameters our model describes a large variety of SP dispersions corresponding to observed data.},
  language  = {en}
}
@article{ManassenJbaraAverbukhetal.2022,
  author    = {Manassen, Yishay and Jbara, Moamen and Averbukh, Michael and Hazan, Zion and Henkel, Carsten and Horovitz, Baruch},
  title     = {Tunnel current noise spectra of spins in individual dimers of molecular radicals},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {105},
  journal   = {Physical review : B, Condensed matter and materials physics},
  number    = {23},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2469-9950},
  doi       = {10.1103/PhysRevB.105.235438},
  pages     = {9},
  year      = {2022},
  abstract  = {We report the detection of electron spin resonance (ESR) in individual dimers of the stable free radical 2,2,6,6tetramethyl-piperidine-1-oxyl (TEMPO). ESR is measured by the current fluctuations in a scanning tunneling microscope (ESR-STM method). The multipeak power spectra, distinct from macroscopic data, are assigned to dimers having exchange and Dzyaloshinskii-Moriya interactions in the presence of spin-orbit coupling. These interactions are generated in our model by interfering electronic tunneling pathways from tip to sample via the dimer???s two molecules. This is the first demonstration that tunneling via two spins is a valid mechanism of the ESR-STM method.},
  language  = {en}
}
@article{JelkenHenkelSanter2020,
  author    = {Jelken, Joachim and Henkel, Carsten and Santer, Svetlana},
  title     = {Polarization controlled fine structure of diffraction spots from an optically induced grating},
  series = {Applied physics letters},
  volume    = {116},
  journal   = {Applied physics letters},
  number    = {5},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0003-6951},
  doi       = {10.1063/1.5140067},
  pages     = {4},
  year      = {2020},
  abstract  = {We report on the remote control of the fine structure of a diffraction spot from optically induced dual gratings within a photosensitive polymer film. The material contains azobenzene in the polymer side chains and develops a surface relief under two-beam holographic irradiation. The diffraction of a polarized probe beam is sensitive to the orientation of the azobenzene groups forming a permanently stored birefringence grating within the film. We demonstrate that the fine structure of the probe diffraction spot switches from a Gaussian to a hollow or a hollow to a "Saturn"-like structure by a change in polarization. This makes it potentially useful in photonic devices because the beam shape can be easily inverted by an external stimulus.},
  language  = {en}
}
@article{PapkeYadavalliHenkeletal.2014,
  author    = {Papke, Thomas and Yadavalli, Nataraja Sekhar and Henkel, Carsten and Santer, Svetlana},
  title     = {Mapping a plasmonic hologram with photosensitive polymer films: standing versus propagating waves},
  series = {ACS applied materials \& interfaces},
  volume    = {6},
  journal   = {ACS applied materials \& interfaces},
  number    = {16},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1944-8244},
  doi       = {10.1021/am503501y},
  pages     = {14174 -- 14180},
  year      = {2014},
  abstract  = {We use a photosensitive layer containing azobenzene moieties to map near-field intensity patterns in the vicinity of nanogrids fabricated within a thin silver layer. It is known that azobenzene containing films deform permanently during irradiation, following the pattern of the field intensity. The photosensitive material reacts only to stationary waves whose intensity patterns do not change in time. In this study, we have found a periodic deformation above the silver film outside the nanostructure, even if the latter consists of just one groove. This is in contradiction to the widely accepted viewpoint that propagating surface plasmon modes dominate outside nanogrids. We explain our observation based on an electromagnetic hologram formed by the constructive interference between a propagating surface plasmon wave and the incident light. This hologram contains a stationary intensity and polarization grating that even appears in the absence of the polymer layer.},
  language  = {en}
}
@article{JelkenHenkelSanter2019,
  author    = {Jelken, Joachim and Henkel, Carsten and Santer, Svetlana},
  title     = {Solving an old puzzle: fine structure of diffraction spots from an azo-polymer surface relief grating},
  series = {Applied physics : B, Lasers and optics},
  volume    = {125},
  journal   = {Applied physics : B, Lasers and optics},
  number    = {11},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {0946-2171},
  doi       = {10.1007/s00340-019-7331-8},
  pages     = {11},
  year      = {2019},
  abstract  = {We report on the experimental and theoretical interpretation of the diffraction of a probe beam during inscription of a surface relief grating with an interference pattern into a photo-responsive polymer film. For this, we developed a set-up allowing for the simultaneous recording of the diffraction efficiency (DE), the fine structure of the diffraction spot and the topographical changes, in situ and in real time while the film is irradiated. The time dependence of the DE, as the surface relief deepens, follows a Bessel function exhibiting maxima and minima. The size of the probe beam relative to the inscribed grating (i.e., to the size of the writing beams) matters and has to be considered for the interpretation of the DE signal. It is also at the origin of a fine structure within the diffraction spot where ring-shaped features appear once an irradiation time corresponding to the first maximum of the DE has been exceeded.},
  language  = {en}
}
@article{JelkenHenkelSanter2020,
  author    = {Jelken, Joachim and Henkel, Carsten and Santer, Svetlana},
  title     = {Formation of half-period surface relief gratings in azobenzene containing polymer films},
  series = {Applied physics : B, Lasers and optics},
  volume    = {126},
  journal   = {Applied physics : B, Lasers and optics},
  number    = {9},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {0946-2171},
  doi       = {10.1007/s00340-020-07500-w},
  pages     = {14},
  year      = {2020},
  abstract  = {We study the peculiar response of photo-sensitive polymer films irradiated with a certain type of interference pattern where one interfering beam is S-polarized, while the second one is P-polarized. The polymer film, although in a glassy state, deforms following the local polarization distribution of the incident light, and a surface relief grating (SRG) appears whose period is half the optical one. All other types of interference patterns result in the matching of both periods. The topographical response is triggered by the alignment of photo-responsive azobenzene containing polymer side chains orthogonal to the local electrical field, resulting in a bulk birefringence grating (BBG). We investigate the process of dual grating formation (SRG and BBG) in a polymer film utilizing a dedicated set-up that combines probe beam diffraction and atomic force microscopy (AFM) measurements, and permits acquiring in situ and in real-time information about changes in local topography and birefringence. We find that the SRG maxima appear at the positions of linearly polarized light (tilted by 45 degrees relative to the grating vector), causing the formation of the half-period topography. This permits to inscribe symmetric and asymmetric topography gratings with sub-wavelength period, while changing only slightly the polarization of one of the interfering beams. We demonstrate an easy generation of sawtooth profiles (blazed gratings) with adjustable shape. With these results, we have taken a significant step in understanding the photo-induced deformation of azo-polymer films.},
  language  = {en}
}
@article{HerzogvonReppertPudelletal.2022,
  author    = {Herzog, Marc and von Reppert, Alexander and Pudell, Jan-Etienne and Henkel, Carsten and Kronseder, Matthias and Back, Christian H. and Maznev, Alexei A. and Bargheer, Matias},
  title     = {Phonon-dominated energy transport in purely metallic heterostructures},
  series = {Advanced functional materials},
  volume    = {32},
  journal   = {Advanced functional materials},
  number    = {41},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1616-301X},
  doi       = {10.1002/adfm.202206179},
  pages     = {8},
  year      = {2022},
  abstract  = {Ultrafast X-ray diffraction is used to quantify the transport of energy in laser-excited nanoscale gold-nickel (Au-Ni) bilayers. Electron transport and efficient electron-phonon coupling in Ni convert the laser-deposited energy in the conduction electrons within a few picoseconds into a strong non-equilibrium between hot Ni and cold Au phonons at the bilayer interface. Modeling of the subsequent equilibration dynamics within various two-temperature models confirms that for ultrathin Au films, the thermal transport is dominated by phonons instead of conduction electrons because of the weak electron-phonon coupling in Au.},
  language  = {en}
}
@article{HovhannisyanNematiHenkeletal.2023,
  author    = {Hovhannisyan, Karen V. and Nemati, Somayyeh and Henkel, Carsten and Anders, Janet},
  title     = {Long-time equilibration can determine transient thermality},
  series = {PRX Quantum},
  volume    = {4},
  journal   = {PRX Quantum},
  number    = {3},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2691-3399},
  doi       = {10.1103/PRXQuantum.4.030321},
  pages     = {23},
  year      = {2023},
  abstract  = {When two initially thermal many-body systems start to interact strongly, their transient states quickly become non-Gibbsian, even if the systems eventually equilibrate. To see beyond this apparent lack of structure during the transient regime, we use a refined notion of thermality, which we call g-local. A system is g-locally thermal if the states of all its small subsystems are marginals of global thermal states. We numerically demonstrate for two harmonic lattices that whenever the total system equilibrates in the long run, each lattice remains g-locally thermal at all times, including the transient regime. This is true even when the lattices have long-range interactions within them. In all cases, we find that the equilibrium is described by the generalized Gibbs ensemble, with three-dimensional lattices requiring special treatment due to their extended set of conserved charges. We compare our findings with the well-known two-temperature model. While its standard form is not valid beyond weak coupling, we show that at strong coupling it can be partially salvaged by adopting the concept of a g-local temperature.},
  language  = {en}
}