Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 30: Surface Magnetism (joint session O/MA)

O 30.10: Vortrag

Dienstag, 2. April 2019, 12:45–13:00, H37

Disentangling the double-exchange and superexchange interactions in quantum anomalous Hall insulators — •Thiago R. F. Peixoto1, Hendrik Bentmann1, Abdul-Vakhab Tcakaev2, Philipp Rüssmann3, Raphael Crespo Vidal1, Sonja Schatz1, Fabian Stier2, Volodymyr Zabolotnyy2, Martin Winnerlein4, Steffen Schreyeck4, Charles Gould4, Karl Brunner4, Stefan Blügel3, Laurens W. Molenkamp4, Vladimir Hinkov2, and Friedrich Reinert11Experimentelle Physik VII, Universität Würzburg — 2Experimentelle Physik IV, Universität Würzburg — 3Peter Grünberg Institut (PGI-1), Forschungszentrum Jülich — 4Experimentelle Physik III, Universität Würzburg

We report on the electronic origin of the magnetic properties of the quantum Hall insulators (V,Cr):(Bi,Sb)2Te3. By combining x-ray magnetic circular dichroism (XMCD), resonant photoemission spectroscopy (resPES) and density functional theory (DFT), we trace element-specific fingerprints in the valence band and magnetic coupling mechanisms. Our results show that while the low spectral weight of Cr 3d states at the Fermi level (EF) support the presence of ferromagnetic superexchange interactions, an additional double-exchange interaction is intimately related to a highly localised V 3d impurity band at EF. Furthermore, we show that a Bi-rich host increases the covalency of the transition metal ions, thereby mitigating Hund’s rule stabilisation. The competition between charge-transfer and pd-exchange ultimately determines the magnetic ground-state in these systems [1].
[1] Larson and Lambrecht, Phys. Rev. B 78, 195207 (2008).

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