Groupe de Physique Statistique

Equipe 106, Institut Jean Lamour

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Séminaire de groupe

 Spin-dependent thermoelectric transport in HgTe/CdTe quantum wells Marine Guigou LPS Orsay/Paris-Sud jeudi 07 février 2013 , 14h00 Salle de séminaire du groupe de Physique Statistique 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 shall 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 shall 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 boudaries [3] .
[1] R. Takahashi and S. Murakami, Phys. Rev. B81, 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. B86, 165434 (2012).