Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 38: Topological Insulators (jointly with HL, MA, TT)
O 38.6: Talk
Wednesday, March 13, 2013, 10:30–10:45, H16
Quasiparticle study of the bulk topological insulators Bi2Se3, Bi2Te3, and Sb2Te3 including spin-orbit coupling. — •Irene Aguilera, Christoph Friedrich, Gustav Bihlmayer, and Stefan Blügel — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
We present GW calculations of the topological insulators Bi2Se3 and Bi2Te3 within the all-electron FLAPW formalism and compare them with previous calculations. We extend the study to the topological insulator Sb2Te3, which poses additional problems when studied with GW based on non-relativistic density functional theory (DFT) as it exhibits a negative DFT band gap. In contrast to the previous GW calculations, we fully take into account spin-orbit coupling (SOC) allowing spin-off-diagonal elements in the Green function and the self-energy, and we discuss the differences to a simpler perturbative approach (i.e., treating SOC on DFT level a posteriori). Additionally, we show that the inclusion of SOC induces fundamental changes in the Green function G, whereas changes in the screened interaction W are negligible. We also discuss the influence of off-diagonal elements of the self-energy matrix.
After inclusion of quasiparticle effects, we observe a direct band gap at the Γ point for Bi2Se3, in disagreement with predictions from DFT but in accordance with experiment. For all compounds, in the most critical case of the band-inversion region around the Γ point, we show that the GW effective masses are significantly different from DFT ones.
Funding was provided by the Alexander von Humboldt Foundation.