@article{SessiBiswasBathonetal.2016,
  author    = {Sessi, Paolo and Biswas, Rudro R. and Bathon, Thomas and Storz, Oliver and Wilfert, Stefan and Barla, Alessandro and Kokh, Konstantin A. and Tereshchenko, Oleg E. and Fauth, Kai and Bode, Matthias and Balatsky, Alexander V.},
  title     = {Dual nature of magnetic dopants and competing trends in topological insulators},
  series = {Nature Communications},
  volume    = {7},
  journal   = {Nature Communications},
  doi       = {10.1038/ncomms12027},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172704},
  year      = {2016},
  abstract  = {Topological insulators interacting with magnetic impurities have been reported to host several unconventional effects. These phenomena are described within the framework of gapping Dirac quasiparticles due to broken time-reversal symmetry. However, the overwhelming majority of studies demonstrate the presence of a finite density of states near the Dirac point even once topological insulators become magnetic. Here, we map the response of topological states to magnetic impurities at the atomic scale. We demonstrate that magnetic order and gapless states can coexist. We show how this is the result of the delicate balance between two opposite trends, that is, gap opening and emergence of a Dirac node impurity band, both induced by the magnetic dopants. Our results evidence a more intricate and rich scenario with respect to the once generally assumed, showing how different electronic and magnetic states may be generated and controlled in this fascinating class of materials.},
  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}
}