Optically monitored nuclear spin dynamics in individual GaAs quantum dots grown by droplet epitaxy

TL;DR

This study demonstrates optical control and measurement of nuclear spin dynamics in individual GaAs quantum dots, revealing bistability and a build-up time of about one second, advancing quantum dot spintronics understanding.

Contribution

It provides the first direct measurement of nuclear polarization build-up time in individual GaAs quantum dots grown by droplet epitaxy.

Findings

Nuclear polarization is bistable in GaAs quantum dots.

The build-up time of nuclear polarization is approximately one second.

Optical orientation yields strong circular polarization at 4K.

Abstract

We report optical orientation experiments in individual, strain free GaAs quantum dots in AlGaAs grown by droplet epitaxy. Circularly polarized optical excitation yields strong circular polarization of the resulting photoluminescence at 4K. Optical injection of spin polarized electrons into a dot gives rise to dynamical nuclear polarization that considerably changes the exciton Zeeman splitting (Overhauser shift). We show that the created nuclear polarization is bistable and present a direct measurement of the build-up time of the nuclear polarization in a single GaAs dot in the order of one second.