Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots

TL;DR

This paper demonstrates that even weak spin-orbit coupling in GaAs quantum dots can significantly suppress dynamic nuclear polarization, revealing a competitive interaction between spin-orbit and hyperfine effects in quantum spin systems.

Contribution

It provides experimental evidence that spin-orbit coupling quenches DNP in GaAs quantum dots and distinguishes its effects from hyperfine interactions using Landau-Zener sweeps.

Findings

Spin-orbit coupling suppresses DNP in GaAs quantum dots.

The effect depends on the strength and direction of the magnetic field.

DNP quenching occurs when spin-orbit effects surpass hyperfine interactions.

Abstract

The central-spin problem, in which an electron spin interacts with a nuclear spin bath, is a widely studied model of quantum decoherence. Dynamic nuclear polarization (DNP) occurs in central spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in spin-based quantum information processing for coherent electron and nuclear spin control. However, the mechanisms limiting DNP remain only partially understood. Here, we show that spin-orbit coupling quenches DNP in a GaAs double quantum dot, even though spin-orbit coupling in GaAs is weak. Using Landau-Zener sweeps, we measure the dependence of the electron spin-flip probability on the strength and direction of in-plane magnetic field, allowing us to distinguish effects of the spin-orbit and hyperfine interactions. To confirm our interpretation, we measure high-bandwidth correlations in the electron spin-flip probability and attain results consistent with a significant spin-orbit contribution. We observe that DNP is quenched when the spin-orbit component exceeds the hyperfine, in agreement with a theoretical model. Our results shed new light on the surprising competition between the spin-orbit and hyperfine interactions in central-spin systems.