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HL: Fachverband Halbleiterphysik

HL 51: Topological Insulators II (jointly with MA, DS, O, TT)

HL 51.6: Vortrag

Mittwoch, 28. März 2012, 10:45–11:00, EB 301

Topological phase transitions in Bi(111) bilayer by breaking time-reversal symmetry — •Hongbin Zhang, Frank Freimuth, Gustav Bihlmayer, Stefan Blügel, and Yuriy Mokrousov — Peter Grünberg Institut & Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

Time-reversal breaking brings forth many novel phenomena in topological insulators [1]. In this work, using the first principles FLAPW method combined with the Wannier functions technique [2], we investigated topological phase transitions with respect to exchange fields of a two-dimensional topological insulator – Bi(111) bilayer [3]. Numerical evaluation of the spin Chern number [4] for different magnitudes of exchange fields reveals that when the time reversal symmetry is broken by a small exchange field, the system keeps the properties of a topological insulator. After a metallic phase in the intermediate region, the quantum anomalous Hall phase with the non-zero Chern number occurs at sufficiently large enough exchange fields. We analyzed the relation between the spin Chern number, the Z₂ number and the Chern number, and also the phase diagram from the viewpoint of the evolution of the electronic structure, edge states and transport properties in this system. We acknowledge funding under HGF-YIG Programme VH-NG-513.

[1] X. Qi, et al., Phys. Rev. B. 78, 195424 (2008).
www.flapw.de; F. Freimuth, et al., Phys. Rev. B. 78, 035120 (2008).
M. Wada, et al., Phys. Rev. B 83, 121310(R) (2011).
E. Prodan, et al., Phys. Rev. B 80, 125327 (2009).