Confinement-induced Berry phase and helicity-dependent photocurrents

TL;DR

This paper investigates how quantum confinement in wells induces a Berry phase that affects helicity-dependent photocurrents, revealing a new mechanism for optical activity in non-optically active materials.

Contribution

It demonstrates that confinement-induced Berry phases can generate helicity-dependent photocurrents, extending understanding of optical effects in quantum wells.

Findings

Berry phase contribution depends on well width and orientation

The effect is linked to a cubic Berry phase intrinsic to the bulk material

Results suggest the effect may have been observed in experiments

Abstract

The photocurrent in an optically active metal is known to contain a component that switches sign with the helicity of the incident radiation. At low frequencies, this current depends on the orbital Berry phase of the Bloch electrons via the "anomalous velocity" of Karplus and Luttinger. We consider quantum wells in which the parent material, such as GaAs, is not optically active and the relevant Berry phase only arises as a result of quantum confinement. Using an envelope approximation that is supported by numerical tight-binding results, it is shown that the Berry phase contribution is determined for realistic wells by a cubic Berry phase intrinsic to the bulk material, the well width, and the well direction. These results for the magnitude of the Berry-phase effect suggest that it may already have been observed in quantum well experiments.