Regensburg 2019 – wissenschaftliches Programm
MA 4.4: Vortrag
Montag, 1. April 2019, 10:15–10:30, H52
The Z2 topology of bismuth — •Irene Aguilera, Christoph Friedrich, Gustav Bihlmayer, and Stefan Blügel — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
The Z2 topology of bulk and thin films of pure bismuth has been a matter of debate in the last few years. Whereas all first-principles calculations with different levels of sophistication predict a trivial Z2 invariant, a couple of photoemission experiments display surface states that look non-trivial. The discrepancies between theory and experiment were originally attributed to the failure of density functional theory (DFT) in the prediction of band gaps, because the topological or trivial character of Bi depends only on the “sign” of the tiny (∼15 meV) direct band gap at the L point. In  we showed that quasiparticle self-consistent GW (QSGW) calculations support the trivial character. These are, to date, the most accurate calculations for bulk Bi in the literature. However, this did not explain the discrepancy with experiments. In this talk, I will explain, based on QSGW calculations, why the apparent contradiction between theory and experiment is, as a matter of fact, no contradiction, and that the “topologically-looking” experimental surface states are actually compatible with a trivial Z2 invariant. We note that we focus on the Z2 topological character only and not on the high-order topology, recently predicted for Bi.
 I. Aguilera et al., Phys. Rev. B 91, 125129 (2015).
Financial support from the Virtual Institute for Topological Insulators of the Helmholtz Association.