@article{MaassBentmannSeibeletal.2016,
  author    = {Maaß, Henriette and Bentmann, Hendrik and Seibel, Christoph and Tusche, Christian and Eremeev, Sergey V. and Peixoto, Thiago R.F. and Tereshchenko, Oleg E. and Kokh, Konstantin A. and Chulkov, Evgueni V. and Kirschner, J{\"u}rgen and Reinert, Friedrich},
  title     = {Spin-texture inversion in the giant Rashba semiconductor BiTeI},
  series = {Nature Communications},
  volume    = {7},
  journal   = {Nature Communications},
  doi       = {10.1038/ncomms11621},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173769},
  year      = {2016},
  abstract  = {Semiconductors with strong spin-orbit interaction as the underlying mechanism for the generation of spin-polarized electrons are showing potential for applications in spintronic devices. Unveiling the full spin texture in momentum space for such materials and its relation to the microscopic structure of the electronic wave functions is experimentally challenging and yet essential for exploiting spin-orbit effects for spin manipulation. Here we employ a state-of-the-art photoelectron momentum microscope with a multichannel spin filter to directly image the spin texture of the layered polar semiconductor BiTeI within the full two-dimensional momentum plane. Our experimental results, supported by relativistic ab initio calculations, demonstrate that the valence and conduction band electrons in BiTeI have spin textures of opposite chirality and of pronounced orbital dependence beyond the standard Rashba model, the latter giving rise to strong optical selection-rule effects on the photoelectron spin polarization. These observations open avenues for spin-texture manipulation by atomic-layer and charge carrier control in polar semiconductors.},
  language  = {en}
}
@article{PeixotoBentmannRuessmannetal.2020,
  author    = {Peixoto, Thiago R. F. and Bentmann, Hendrik and R{\"u}ßmann, Philipp and Tcakaev, Abdul-Vakhab and Winnerlein, Martin and Schreyeck, Steffen and Schatz, Sonja and Vidal, Raphael Crespo and Stier, Fabian and Zabolotnyy, Volodymyr and Green, Robert J. and Min, Chul Hee and Fornari, Celso I. and Maaß, Henriette and Vasili, Hari Babu and Gargiani, Pierluigi and Valvidares, Manuel and Barla, Alessandro and Buck, Jens and Hoesch, Moritz and Diekmann, Florian and Rohlf, Sebastian and Kall{\"a}ne, Matthias and Rossnagel, Kai and Gould, Charles and Brunner, Karl and Bl{\"u}gel, Stefan and Hinkov, Vladimir and Molenkamp, Laurens W. and Friedrich, Reinert},
  title     = {Non-local effect of impurity states on the exchange coupling mechanism in magnetic topological insulators},
  series = {NPJ Quantum Materials},
  volume    = {5},
  journal   = {NPJ Quantum Materials},
  doi       = {10.1038/s41535-020-00288-0},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230686},
  year      = {2020},
  abstract  = {Since the discovery of the quantum anomalous Hall (QAH) effect in the magnetically doped topological insulators (MTI) Cr:(Bi,Sb)\(_2\)Te\(_3\) and V:(Bi,Sb)\(_2\)Te\(_3\), the search for the magnetic coupling mechanisms underlying the onset of ferromagnetism has been a central issue, and a variety of different scenarios have been put forward. By combining resonant photoemission, X-ray magnetic circular dichroism and density functional theory, we determine the local electronic and magnetic configurations of V and Cr impurities in (Bi,Sb)\(_2\)Te\(_3\). State-of-the-art first-principles calculations find pronounced differences in their 3d densities of states, and show how these impurity states mediate characteristic short-range pd exchange interactions, whose strength sensitively varies with the position of the 3d states relative to the Fermi level. Measurements on films with varying host stoichiometry support this trend. Our results explain, in an unified picture, the origins of the observed magnetic properties, and establish the essential role of impurity-state-mediated exchange interactions in the magnetism of MTI.},
  language  = {en}
}