Spin polarized photocurrent from quantum dots

TL;DR

This paper demonstrates that increasing light intensity can switch the spin polarization of photocurrent in quantum dot photodiodes via a nonlinear exchange interaction, enabling dynamic control of spin-polarized electrons.

Contribution

It introduces a novel method to dynamically invert spin polarization in quantum dots using elliptically polarized light intensity.

Findings

Spin polarization can be switched by increasing light intensity.

The effect persists in ensembles of quantum dots.

The mechanism involves an effective exchange interaction through the biexciton state.

Abstract

In this paper we show that it is possible to switch the spin polarization of the photocurrent signal obtained from a single self-assembled quantum dot photodiode under the effect of elliptically polarized light by just increasing the light intensity. In the nonlinear mechanism treated here, intense elliptically polarized light creates an effective exchange interaction between the exciton spin states through the biexciton state. This effect can be used as a dynamical switch to invert the spin-polarization of the extracted photocurrent. We further show that the effect persists in realistic ensembles of dots, making this a powerful technique to dynamically generate spin-polarized electrons.