Diffusion at the Surface of Topological Insulators

TL;DR

This paper investigates how hexagonal warping affects the surface state transport in topological insulators, revealing non-perturbative effects on diffusion and conductance fluctuations with implications for experiments.

Contribution

Develops a non-perturbative framework to analyze the impact of hexagonal warping on topological insulator surface state transport, surpassing previous perturbative approaches.

Findings

Diffusion constant strongly depends on Fermi energy due to warping.

Hexagonal warping attenuates conductance fluctuations when combined with Zeeman effect.

Perturbative analysis fails for realistic topological insulators like Bi2Se3.

Abstract

We consider the transport properties of topological insulators surface states in the presence of uncorrelated point-like disorder, both in the classical and quantum regimes. The transport properties of those two-dimensional surface states depend strongly on the amplitude of the hexagonal warping of their Fermi surface. It is shown that a perturbative analysis of the warping fails to describe the transport in experimentally available topological insulators, such as Bi2Se3 and Bi2Te3. Hence we develop a fully non-perturbative description of these effects. In particular, we find that the dependence of the warping amplitude on the Fermi energy manifests itself in a strong dependence of the diffusion constant on this Fermi energy, leading to several important experimental consequences. Moreover, the combination of a strong warping with an in plane Zeeman effect leads to an attenuation of conductance fluctuations in contrast to the situation of unwarped Dirac surface states.