Photogalvanic effect in HgTe/CdTe topological insulator due to edge-bulk optical transitions

TL;DR

This paper theoretically predicts a circular photocurrent in HgTe/CdTe topological insulators caused by edge-bulk optical transitions under circularly polarized light, revealing a new spin-dependent photogalvanic effect.

Contribution

It introduces the concept of a photogalvanic effect driven by edge-bulk transitions in topological insulators, highlighting the role of electron-hole asymmetry and spin-dependent dipole transitions.

Findings

Electron-hole asymmetry induces spin-dependent edge-bulk optical transitions.

Circularly polarized light generates a measurable photocurrent in the TI.

Photocurrent can be detected via electromotive force in an attached conductor.

Abstract

We study theoretically 2D HgTe/CdTe quantum well topological insulator (TI) illuminated by circularly polarized light with frequencies higher than the difference between the equilibrium Fermi level and the bottom of the conduction band (THz range). We show that electron-hole asymmetry results in spin-dependent electric dipole transitions between edge and bulk states, and we predict an occurrence of a circular photocurrent. If the edge state is tunnel-coupled to a conductor, then the photocurrent can be detected by measuring an electromotive force (EMF) in the conductor, which is proportional to the photocurrent.