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Steffen Wiedmann: HgTe as a topological insulator

Wanneer:ma 30-05-2016 13:00 - 12:00

In this presentation, I will introduce the material system of mercury-telluride (HgTe) as a proto-type for the investigation of topological transport properties in two-dimensional (2D) and three-dimensional (3D) systems. HgTe is a zincblende-type semiconductor with an inverted band structure. While the bulk material is a semimetal, lowering the crystalline symmetry opens up a gap, turning the system into a topological insulator (TI). HgTe/CdTe quantum wells (QWs) are known to be the first realization of a 2D TI [1]. Due to their relativistic Landau level dispersion, the Quantum Hall effect can be observed almost up to nitrogen temperatures [2]. The high electronic quality of 3D TIs based on strained HgTe allows a direct observation of the surface quantum Hall effect. Furthermore, the thermoelectric power of the electron-like surface states is diffusion driven in contrast to hole-like surface carriers where both diffusion and phonon drag are essential [3].

[1] M. König et al., Science 318, 766 (2007).                                                                                                         [2] T. Khouri et al., Phys. Rev. B 93, 125308.                                                                                           [3] A. Jost et al., submitted for publication.