Photogalvanic effects in topological insulators

TL;DR

This paper explores how circularly polarized light induces electric currents in topological insulators, revealing potential for optoelectronic applications by analyzing photoelectric effects both in the bulk and edge states.

Contribution

It provides a theoretical analysis of photogalvanic effects in topological insulators, highlighting mechanisms for current generation via magnetic and electric dipole transitions.

Findings

Circularly polarized light induces edge currents in 2D topological insulators.

Two mechanisms for current induction: magnetic dipole transitions below the gap and electric dipole transitions above the gap.

Photogenerated carriers can be captured on edge states, enabling optoelectronic control.

Abstract

We discuss optical absorption in topological insulators and study possible photoelectric effects theoretically. We found that absorption of circularly polarized electromagnetic waves in two-dimensional topological insulators results in electric current in the conducting 1D edge channels, the direction of the current being determined by the light polarization. We suggest two ways of inducing such a current: due to magnetic dipole electron transitions stimulated by irradiation of frequency below the bulk energy gap, and due to electric dipole transitions in the bulk at frequencies larger than the energy gap with subsequent capture of the photogenerated carriers on conducting edge states.