Berlin 2015 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 23: Topological insulators: Theory (HL with DS/MA/O/TT)
DS 23.5: Vortrag
Mittwoch, 18. März 2015, 10:30–10:45, ER 270
Topological states in α-Sn and HgTe quantum wells: a comparison of ab-initio results — •Sebastian Küfner and Friedhelm Bechstedt — Friedrich Schiller Universität Jena
Quantum well (QW) structures based on HgTe are theroretically predicted and experimentally verified to exhibit the quantum-spin Hall phase. Despite the similarities of the bulk band structures, studies of α-Sn QW structures are missing. We compare the properties of QW structures made by the different zero-gap semiconductors α-Sn and HgTe, but both sandwiched in nearly lattice-matched CdTe barriers by means of first-principles calculations including quasiparticle corrections and spin-orbit interaction. The two well materials possess different space groups Oh7 (diamond structure) and Td2 (zinc-blende structure). The spin-orbit interaction, in particular that in the p-derived valence states, is different due to the contribution of both atoms in the unit cell (α-Sn) and mainly the anion (HgTe) to the states at the top of the valence bands, and the different local electrostatic properties due to the different bonding character in the QW layers and their interfaces with the CdTe barrier material. We investigate the similarities and differences of the two embedded zero-gap semiconductors on the formation of quantum-well, edge and interface states in detail.