Regensburg 2016 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 55: Frontiers of Electronic Structure Theory: Focus on Topology and Transport III
(Joint session of DS, HL, MA, MM, O and TT organized by O)
TT 55.6: Vortrag
Mittwoch, 9. März 2016, 16:45–17:00, H24
Two-dimensional topological phases and electronic spectra of topological insulator thin films from GW calculations — •Tobias Förster, Peter Krüger, and Michael Rohlfing — Institut für Festkörpertheorie, Westfälische Wilhelms-Universität, 48149 Münster, Germany
We have investigated topological and electronic properties of thin films of the topological insulators Bi2Se3, Bi2Te3, and Sb2Te3 with thicknesses from one to six quintuple layers employing the GW method. The quasiparticle band structures show highly improved agreement with experiments compared to DFT. In addition to a correction of the band gaps, the energetic positions and dispersions of the surface states change significantly around Γ [1]. The common approach of taking the diagonal elements of the self-energy Σ as quasiparticle energies and leaving the wave functions unchanged yields unphysical results which can be overcome by diagonalizing HQP. The origin of the respective off-diagonal elements in (Σ − Vxc) will be discussed. As the wave functions are updated, the two-dimensional topological phases (quantum spin Hall or trivial) in GW differ from DFT for many systems. On the basis of our results, we further argue that one cannot unambiguously conclude the topological phase from fits to ARPES band structures as performed in recent experimental studies.
[1] T. Förster, P. Krüger, and M. Rohlfing, Phys. Rev. B 92, 201404(R) (2015)