TY  - JOUR
A1  - Peixoto, Thiago R. F.
A1  - Bentmann, Hendrik
A1  - Rüßmann, Philipp
A1  - Tcakaev, Abdul-Vakhab
A1  - Winnerlein, Martin
A1  - Schreyeck, Steffen
A1  - Schatz, Sonja
A1  - Vidal, Raphael Crespo
A1  - Stier, Fabian
A1  - Zabolotnyy, Volodymyr
A1  - Green, Robert J.
A1  - Min, Chul Hee
A1  - Fornari, Celso I.
A1  - Maaß, Henriette
A1  - Vasili, Hari Babu
A1  - Gargiani, Pierluigi
A1  - Valvidares, Manuel
A1  - Barla, Alessandro
A1  - Buck, Jens
A1  - Hoesch, Moritz
A1  - Diekmann, Florian
A1  - Rohlf, Sebastian
A1  - Kalläne, Matthias
A1  - Rossnagel, Kai
A1  - Gould, Charles
A1  - Brunner, Karl
A1  - Blügel, Stefan
A1  - Hinkov, Vladimir
A1  - Molenkamp, Laurens W.
A1  - Friedrich, Reinert
T1  - Non-local effect of impurity states on the exchange coupling mechanism in magnetic topological insulators
JF  - NPJ Quantum Materials
N2  - 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.
KW  - shape-truncation functions
KW  - semiconductors
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230686
VL  - 5
ER  - 
TY  - JOUR
A1  - Min, Chul-Hee
A1  - Goth, F.
A1  - Lutz, P.
A1  - Bentmann, H.
A1  - Kang, B.Y.
A1  - Cho, B.K.
A1  - Werner, J.
A1  - Chen, K.-S.
A1  - Assaad, F.
A1  - Reinert, F.
T1  - Matching DMFT calculations with photoemission spectra of heavy fermion insulators: universal properties of the near-gap spectra of SmB\(_{6}\)
JF  - Scientific Reports
N2  - Paramagnetic heavy fermion insulators consist of fully occupied quasiparticle bands inherent to Fermi liquid theory. The gap emergence below a characteristic temperature is the ultimate sign of coherence for a many-body system, which in addition can induce a non-trivial band topology. Here, we demonstrate a simple and efficient method to compare a model study and an experimental result for heavy fermion insulators. The temperature dependence of the gap formation in both local moment and mixed valence regimes is captured within the dynamical mean field (DMFT) approximation to the periodic Anderson model (PAM). Using the topological coherence temperature as the scaling factor and choosing the input parameter set within the mixed valence regime, we can unambiguously link the theoretical energy scales to the experimental ones. As a particularly important result, we find improved consistency between the scaled DMFT density of states and the photoemission near-gap spectra of samarium hexaboride (SmB\(_{6}\)).
KW  - SmB\(_{6}\)
KW  - heavy fermion insulators
KW  - dynamical mean field
KW  - samarium hexaboride
KW  - near-gap spectra
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170328
VL  - 7
IS  - 11980
ER  -