Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 26: Transport: Topological Insulators 3 (jointly with HL and MA)

TT 26.1: Talk

Wednesday, March 28, 2012, 09:30–09:45, BH 334

Spin-dependent thermoelectric transport in topological insulators — •Dietrich G. Rothe, Marine Guigou, Björn Trauzettel, and Ewelina M. Hankiewicz — Institut für Theoretische Phys. und Astrophys. Würzburg

We analyze spin-dependent thermoelectric transport of topological insulators based on (Hg,Cd)Te quantum wells using the non-equilibrium Green's function technique within the Bernevig-Hughes-Zhang model. The motivation for our work is to generate spin currents in a medium with strong spin orbit coupling by a gradient of temperature in the absence of magnetic fields. Furthermore, we would like to better understand to what extend the thermoelectric coefficients probe spectral properties of such devices.

We investigate specifically the spin Nernst effect, a transverse spin current induced by a longitudinal temperature gradient, in a four-terminal setup. Interestingly, we predict a peak in the spin Nernst signal when the device is operated in the topologically non-trivial regime. This peak is directly related to the minigap formed by overlapping edge states from opposite boundaries of our device. Hence, the spin Nernst effect is a powerful experimental tool to analyze the size and the structure of the minigap. Additionally, we see that the spin Nernst effect is rather sensitive to details of the band structure. We discuss how this effect can be used to distinguish the topologically trivial from the non-trivial regime and why the energy dependence of transport is markedly resolved in the experimental signatures of the spin Nernst signal.