Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 56: Focussed Session: Frontiers of Electronic Structure Theory - Non-equilibrium Phenomena at the Nano-scale V

O 56.3: Talk

Wednesday, April 2, 2014, 16:45–17:00, TRE Ma

Quasiparticle self-consistent GW method with spin-orbit coupling applied to Bi and HgTe — •Christoph Friedrich, Irene Aguilera, Markus Betzinger, and Stefan Blügel — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

We present an implementation of the quasiparticle self-consistent (QS) GW method where the spin-orbit coupling (SOC) is fully taken into account in each iteration rather than being added a posteriori. The implementation is based on the FLAPW method. The SOC gives rise to spin off-diagonal blocks in the Green function G^SOC and the self-energy Σ^SOC=iG^SOCW^SOC. We applied the QSG^SOCW^SOC method to the semimetal Bi, which presents in experiment small electron and hole pockets and a tiny band gap (11-15 meV) at the L point, all of them largely overestimated by LDA (e.g., the gap is 86 meV). The QSG^SOCW^SOC approach predicts a value of the band gap of 8 meV and electron and hole pockets in very good agreement with experiment. The a posteriori treatment of the SOC (QSGW+SOC), on the other hand, yields an unphysical result for Bi, predicting it to be a topological insulator with a very large gap at L (260 meV) instead of a trivial semimetal. Similarly, for HgTe, QSGW+SOC reorders the bands in a wrong way and opens a gap at the Γ point in disagreement with experiment. In contrast, the QSG^SOCW^SOC approach yields a qualitatively and quantitatively correct description of the electronic band structure. We acknowledge support from the Helmholtz Association through the Virtual Institute for Topological Insulators (VITI).