@article{KoenneckeFollathPontiusetal.2013,
  author    = {K{\"o}nnecke, Rene and Follath, R. and Pontius, N. and Schlappa, J. and Eggenstein, F. and Zeschke, T. and Bischoff, P. and Schmidt, J. -S. and Noll, T. and Trabant, C. and Schreck, S. and Wernet, Ph. and Eisebitt, S. and Senf, F. and Schuessler-Langeheine, Christian and Erko, A. and F{\"o}hlisch, Alexander},
  title     = {The confocal plane grating spectrometer at BESSY II},
  series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy},
  volume    = {188},
  journal   = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0368-2048},
  doi       = {10.1016/j.elspec.2012.11.003},
  pages     = {133 -- 139},
  year      = {2013},
  abstract  = {At BESSY II a confocal plane grating spectrometer for resonant inelastic X-ray scattering (RIXS) is currently under commissioning. The new endstation operates with a source size of 4 x 1 mu m(2) provided by its dedicated beamline. The RIXS-spectrometer covers an energy range from 50 eV to 1000 eV, providing a resolving power E/Delta E of 5000-15,000. The beamline allows full polarization control and gives a photon flux of up to 7 x 10(14) photons/s/0.1 A/0.1\%bandwidth by offering a resolving power E/Delta E of 4000-12,000.},
  language  = {en}
}
@article{BeyeSchreckSorgenfreietal.2013,
  author    = {Beye, Martin and Schreck, S. and Sorgenfrei, Florian and Trabant, C. and Pontius, N. and Sch{\"u}ßler-Langeheine, C. and Wurth, W. and F{\"o}hlisch, Alexander},
  title     = {Stimulated X-ray emission for materials science},
  series = {Nature : the international weekly journal of science},
  volume    = {501},
  journal   = {Nature : the international weekly journal of science},
  number    = {7466},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {0028-0836},
  doi       = {10.1038/nature12449},
  pages     = {191 -- +},
  year      = {2013},
  abstract  = {Resonant inelastic X-ray scattering and X-ray emission spectroscopy can be used to probe the energy and dispersion of the elementary low-energy excitations that govern functionality in matter: vibronic, charge, spin and orbital excitations(1-7). A key drawback of resonant inelastic X-ray scattering has been the need for high photon densities to compensate for fluorescence yields of less than a per cent for soft X-rays(8). Sample damage from the dominant non-radiative decays thus limits the materials to which such techniques can be applied and the spectral resolution that can be obtained. A means of improving the yield is therefore highly desirable. Here we demonstrate stimulated X-ray emission for crystalline silicon at photon densities that are easily achievable with free-electron lasers(9). The stimulated radiative decay of core excited species at the expense of non-radiative processes reduces sample damage and permits narrow-bandwidth detection in the directed beam of stimulated radiation. We deduce how stimulated X-ray emission can be enhanced by several orders of magnitude to provide, with high yield and reduced sample damage, a superior probe for low-energy excitations and their dispersion in matter. This is the first step to bringing nonlinear X-ray physics in the condensed phase from theory(10-16) to application.},
  language  = {en}
}
@article{deJongKukrejaTrabantetal.2013,
  author    = {de Jong, S. and Kukreja, R. and Trabant, C. and Pontius, N. and Chang, C. F. and Kachel, T. and Beye, Martin and Sorgenfrei, Florian and Back, C. H. and Braeuer, B. and Schlotter, W. F. and Turner, J. J. and Krupin, O. and Doehler, M. and Zhu, D. and Hossain, M. A. and Scherz, A. O. and Fausti, D. and Novelli, F. and Esposito, M. and Lee, W. S. and Chuang, Y. D. and Lu, D. H. and Moore, R. G. and Yi, M. and Trigo, M. and Kirchmann, P. and Pathey, L. and Golden, M. S. and Buchholz, Marcel and Metcalf, P. and Parmigiani, F. and Wurth, W. and F{\"o}hlisch, Alexander and Schuessler-Langeheine, Christian and Duerr, H. A.},
  title     = {Speed limit of the insulator-metal transition in magnetite},
  series = {Nature materials},
  volume    = {12},
  journal   = {Nature materials},
  number    = {10},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {1476-1122},
  doi       = {10.1038/NMAT3718},
  pages     = {882 -- 886},
  year      = {2013},
  abstract  = {As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown(1), magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator-metal, or Verwey, transition has long remained inaccessible(2-8). Recently, three- Fe- site lattice distortions called trimeronswere identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase(9). Here we investigate the Verwey transition with pump- probe X- ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator-metal transition. We find this to be a two- step process. After an initial 300 fs destruction of individual trimerons, phase separation occurs on a 1.5 +/- 0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics(10).},
  language  = {en}
}