Anomalous galvanomagnetism, cyclotron resonance and microwave spectroscopy of topological insulators

TL;DR

This paper investigates how external magnetic fields can suppress bulk conductivity in topological insulators, revealing anomalies in galvanomagnetic and electromagnetic responses that indicate the surface quantum Hall state.

Contribution

It proposes a method to detect the surface quantum Hall state by analyzing magnetic field-dependent anomalies in galvanomagnetic and microwave responses.

Findings

Linear bulk dc magnetoresistivity observed.

Quadratic field dependence of Hall angle identified.

Saturation of Faraday rotation angle with field or frequency.

Abstract

The surface quantum Hall state, magneto-electric phenomena and their connection to axion electrodynamics have been studied intensively for topological insulators. One of the obstacles for observing such effects comes from nonzero conductivity of the bulk. To overcome this obstacle we propose to use an external magnetic field to suppress the conductivity of the bulk carriers. The magnetic field dependence of galvanomagnetic and electromagnetic responses of the whole system shows anomalies due to broken time-reversal symmetry of the surface quantum Hall state, which can be used for its detection. In particular, we find linear bulk dc magnetoresistivity and a quadratic field dependence of the Hall angle, shifted rf cyclotron resonance, nonanalytic microwave transmission coefficient and saturation of the Faraday rotation angle with increasing magnetic field or wave frequency.