Electric and thermoelectric transport in graphene and helical metal in finite magnetic fields

TL;DR

This paper investigates electrical and thermoelectric transport in graphene and topological insulator surface states under magnetic fields, highlighting the effects of impurities and spin-momentum coupling on transport properties.

Contribution

It provides numerical and analytical analysis of transport coefficients considering impurity effects and spin coupling, revealing unique signatures in topological insulators.

Findings

Universal peak values of thermopower in clean limit

Dependence of transport on gyromagnetic ratio ($g$) in topological insulators

Distinct signatures due to magnetoelectric coupling in topological insulators

Abstract

We study electrical and thermoelectric transport properties of the surface state of the topological insulator and graphene in the presence of randomly distributed impurities. For finite impurity strength, the dependence of the transport coefficients as a function of gate voltage, magnetic field and impurity potential, are obtained numerically. In the limit of zero impurities (clean limit), analytic results for the peak values of the magneto-oscillations in thermopower are derived. Analogous with the conventional two dimensional electron gas, the peak values are universal in the clean limit. Unlike graphene, in topological insulators the coupling of the electron spin to its momentum leads to a dependence of the transport coefficients on the gyromagnetic ratio ($g$). We compare our results with data on graphene and identify unique signatures expected in topological insulators due to the magnetoelectric coupling.