Asymmetric optical nuclear spin pumping in a single uncharged quantum dot

TL;DR

This study demonstrates highly asymmetric optical nuclear spin pumping in a single quantum dot, revealing strong polarization effects, magnetic field dependencies, and real-time dynamics, advancing understanding of spin interactions at the quantum level.

Contribution

It introduces a detailed model explaining asymmetric nuclear spin polarization driven by hyperfine interactions in a single quantum dot.

Findings

Maximum nuclear polarization of 54% achieved

Pumping efficiency varies with magnetic field, showing resonances

Real-time monitoring of nuclear spin buildup

Abstract

A highly asymmetric dynamic nuclear spin pumping is observed in a single self assembled InGaAs quantum dot subject to resonant optical pumping of the neutral exciton transition leading to a large maximum polarization of 54%. This dynamic nuclear polarization is found to be much stronger following pumping of the higher energy Zeeman state. Time-resolved measurements allow us to directly monitor the buildup of the nuclear spin polarization in real time and to quantitatively study the dynamics of the process. A strong dependence of the observed dynamic nuclear polarization on the applied magnetic field is found, with resonances in the pumping efficiency being observed for particular magnetic fields. We develop a model that fully accounts for the observed behaviour, where the pumping of the nuclear spin system is due to hyperfine-mediated spin flip transitions between the states of the neutral exciton manifold.