Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 53: Transport: Topological Insulators 3 (jointly with TT, MA)
HL 53.9: Talk
Wednesday, March 28, 2012, 11:45–12:00, BH 334
Tunable quantum spin Hall effect in double quantum wells — •Paolo Michetti1, Jan C. Budich1, Elena G. Novik2, and Patrik Recher1,3 — 1Institute of Theoretical Physics and Astrophysics, University of Würzburg, D-97074 Würzburg, Germany — 2Physical Institute, University of Würzburg, D-97074 Würzburg, Germany — 3Institute for Mathematical Physics, TU Braunschweig, 38106 Braunschweig, Germany
The field of topological insulators (TIs) is rapidly growing. The quantum spin Hall effect, characterized by a single pair of helical edge modes protected by time-reversal symmetry, has been demonstrated in HgTe-based quantum wells (QWs) with an inverted bandgap. Concerning possible applications, the quest for materials with an easily controllable TI phase is a key issue.
We analyze, employing an extended version of the Bernevig-Hughes-Zhang model, the topological properties of a generically coupled HgTe-based double QW (DQW). In particular we show how in such a system a TI phase can be driven by an inter-layer bias voltage, even when the individual layers are non-inverted. We also provide a numerical estimate of the system parameters, based on k.p calculations, suggesting the experimental feasibility of the present proposal.
Consequently, a DQW composed of non-inverted QWs, which could be in principle made of suitable narrow gap semiconductors different from HgTe, can be driven into a topologically non-trivial phase with the application of a gate bias.