Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 59: Topological Insulators I (joint session TT/MA)

TT 59.3: Vortrag

Mittwoch, 14. März 2018, 12:15–12:30, A 053

Spin-phonon scattering in edge states of two-dimensional topological insulators — •Solofo Groenendijk, Giacomo Dolcetto, and Thomas Schmidt — Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg

We study theoretically the effect of electron-phonon scattering in 2D topological insulator (2DTI) edge states. Due to the spin-momentum locking in helical edge states, dynamical deformations of the edge modify the spin texture of the electronic edge states. In our work, we show that the resulting spin-phonon coupling ultimately leads to backscattering.

For a short channel, we compute the temperature-dependent conductance in the linear regime (β eV < k_B T) using the Kubo formula, and find δ G ∝ T⁵ for the backscattering conductance. In the limit of a long edge channel, transport becomes diffusive and we compute the resistivity ρ using the semi-classical Boltzmann equation. In particular we find a metallic Bloch-Grüneisen behaviour for chemical potentials near the Dirac point.

Since this spin-phonon coupling arises even in ideal samples and since further imperfections (e.g. Rashba impurities, charge puddles, electron-electron interactions etc.) can only increase backscattering, our results impose a fundamental upper limit on the conductivity of 2D TI edge states.