@article{HlawenkaSiemensmeyerWeschkeetal.2018,
  author    = {Hlawenka, Peter and Siemensmeyer, Konrad and Weschke, Eugen and Varykhalov, Andrei and Sanchez-Barriga, Jaime and Shitsevalova, Natalya Y. and Dukhnenko, A. V. and Filipov, V. B. and Gabani, Slavomir and Flachbart, Karol and Rader, Oliver and Rienks, Emile D. L.},
  title     = {Samarium hexaboride is a trivial surface conductor},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/s41467-018-02908-7},
  pages     = {7},
  year      = {2018},
  abstract  = {SmB6 is predicted to be the first member of the intersection of topological insulators and Kondo insulators, strongly correlated materials in which the Fermi level lies in the gap of a many-body resonance that forms by hybridization between localized and itinerant states. While robust, surface-only conductivity at low temperature and the observation of surface states at the expected high symmetry points appear to confirm this prediction, we find both surface states at the (100) surface to be topologically trivial. We find the (Gamma) over bar state to appear Rashba split and explain the prominent (X) over bar state by a surface shift of the many-body resonance. We propose that the latter mechanism, which applies to several crystal terminations, can explain the unusual surface conductivity. While additional, as yet unobserved topological surface states cannot be excluded, our results show that a firm connection between the two material classes is still outstanding.},
  language  = {en}
}
@misc{HlawenkaSiemensmeyerWeschkeetal.2018,
  author    = {Hlawenka, Peter and Siemensmeyer, Konrad and Weschke, Eugen and Varykhalov, Andrei and S{\´a}nchez-Barriga, Jaime and Shitsevalova, Natalya Y. and Dukhnenko, A.V. and Filipov, V. B. and Gab{\´a}ni, Slavomir and Flachbart, Karol and Rader, Oliver and Rienks, Emile D. L.},
  title     = {Samarium hexaboride is a trivial surface conductor},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {612},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-42421},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-424213},
  pages     = {7},
  year      = {2018},
  abstract  = {SmB6 is predicted to be the first member of the intersection of topological insulators and Kondo insulators, strongly correlated materials in which the Fermi level lies in the gap of a many-body resonance that forms by hybridization between localized and itinerant states. While robust, surface-only conductivity at low temperature and the observation of surface states at the expected high symmetry points appear to confirm this prediction, we find both surface states at the (100) surface to be topologically trivial. We find the (Gamma) over bar state to appear Rashba split and explain the prominent (X) over bar state by a surface shift of the many-body resonance. We propose that the latter mechanism, which applies to several crystal terminations, can explain the unusual surface conductivity. While additional, as yet unobserved topological surface states cannot be excluded, our results show that a firm connection between the two material classes is still outstanding.},
  language  = {en}
}
@article{RienksWimmerSanchezBarrigaetal.2019,
  author    = {Rienks, Emile D. L. and Wimmer, S. and Sanchez-Barriga, Jaime and Caha, O. and Mandal, Partha Sarathi and Ruzicka, J. and Ney, A. and Steiner, H. and Volobuev, V. V. and Groiss, H. and Albu, M. and Kothleitner, G. and Michalicka, J. and Khan, S. A. and Minar, J. and Ebert, H. and Bauer, G. and Freyse, F. and Varykhalov, Andrei and Rader, Oliver and Springholz, G.},
  title     = {Large magnetic gap at the Dirac point in Bi2Te3/MnBi2Te4 heterostructures},
  series = {Nature : the international weekly journal of science},
  volume    = {576},
  journal   = {Nature : the international weekly journal of science},
  number    = {7787},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {0028-0836},
  doi       = {10.1038/s41586-019-1826-7},
  pages     = {423 -- 428},
  year      = {2019},
  abstract  = {Magnetically doped topological insulators enable the quantum anomalous Hall effect (QAHE), which provides quantized edge states for lossless charge-transport applications(1-8). The edge states are hosted by a magnetic energy gap at the Dirac point(2), but hitherto all attempts to observe this gap directly have been unsuccessful. Observing the gap is considered to be essential to overcoming the limitations of the QAHE, which so far occurs only at temperatures that are one to two orders of magnitude below the ferromagnetic Curie temperature, T-C (ref. (8)). Here we use low-temperature photoelectron spectroscopy to unambiguously reveal the magnetic gap of Mn-doped Bi2Te3, which displays ferromagnetic out-of-plane spin texture and opens up only below T-C. Surprisingly, our analysis reveals large gap sizes at 1 kelvin of up to 90 millielectronvolts, which is five times larger than theoretically predicted(9). Using multiscale analysis we show that this enhancement is due to a remarkable structure modification induced by Mn doping: instead of a disordered impurity system, a self-organized alternating sequence of MnBi2Te4 septuple and Bi2Te3 quintuple layers is formed. This enhances the wavefunction overlap and size of the magnetic gap(10). Mn-doped Bi2Se3 (ref. (11)) and Mn-doped Sb2Te3 form similar heterostructures, but for Bi2Se3 only a nonmagnetic gap is formed and the magnetization is in the surface plane. This is explained by the smaller spin-orbit interaction by comparison with Mn-doped Bi2Te3. Our findings provide insights that will be crucial in pushing lossless transport in topological insulators towards room-temperature applications.},
  language  = {en}
}
@article{SajediKrivenkovMarchenkoetal.2020,
  author    = {Sajedi, Maryam and Krivenkov, Maxim and Marchenko, Dmitry and Varykhalov, Andrei and Sanchez-Barriga, Jaime and Rienks, Emile D. L. and Rader, Oliver},
  title     = {Absence of a giant Rashba effect in the valence band of lead halide perovskites},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {102},
  journal   = {Physical review : B, Condensed matter and materials physics},
  number    = {8},
  publisher = {American Institute of Physics; American Physical Society (APS)},
  address   = {Woodbury, NY},
  issn      = {2469-9950},
  doi       = {10.1103/PhysRevB.102.081116},
  pages     = {6},
  year      = {2020},
  abstract  = {For hybrid organic-inorganic as well as all-inorganic lead halide perovskites a Rashba effect has been invoked to explain the high efficiency in energy conversion by prohibiting direct recombination. Both a bulk and surface Rashba effect have been predicted. In the valence band of methylammonium (MA) lead bromide a Rashba effect has been reported by angle-resolved photoemission and circular dichroism with giant values of 7-11 eV angstrom. We present band dispersion measurements of MAPbBr(3) and spin-resolved photoemission of CsPbBr3 to show that a large Rashba effect detectable by photoemission or circular dichroism does not exist and cannot be the origin of the high effciency.},
  language  = {en}
}