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Mardi 12 fevrier 2013-14:00

Spin-dependent thermoelectric transport in HgTe/CdTe quantum wells

Marine Guigou (LPS Orsay)

par Bertrand Georgeot - 12 février 2013

HgTe quantum wells are known to host, under a topological phase transition, the quantum spin Hall effect. The latter refers to the presence of metallic edge states moving in opposite direction for opposite spins. Recently, HgTe/CdTe quantum wells, among others topological insulators, have been proposed as good materials for thermoelectric conversion. The basic idea relies on the topological protection of the 1D edge states that prevents reduction of electrical transport in disordered systems. Their efficiency to convert heat into electricity is based on the dominance of the edge modes on transport [1,2].

During this presentation, I will discuss about the thermoelectric properties of HgTe/CdTe quantum wells through the analysis of Seebeck and spin Nernst coefficents in a four terminal cross-bar setup. As a lateral thermal gradient induces a longitudinal electric bias and a transverse spin current in such a system, each of them can be used as a probe of the topological regime as well as finite size effects of the quantum spin Hall insulator. Furthermore, I will present a qualitative relative between effective mass of particles and magnitude of spin Nernst signal which allows to provide an explanation of the observed phenomena based on anomalous velocities and spin-dependent scattering off boundaries[3]

[1] R. Takahashi and S. Murakami, Phys. Rev. B 81, 161302 (2010).

[2] O.A. Tretiakov, A. Abanov, S. Murakami, and J. Sinova, Appl. Phys. Lett. 97, 073108 (2010).

[3] D.G. Rothe, E.M. Hankiewicz, B. Trauzettel, and M.G., Phys. Rev. B 86, 165434 (2012).

Post-scriptum :

contact : Pierre Pujol