Suppression of Zeeman gradients by nuclear polarization in double quantum dots

TL;DR

This paper demonstrates how dynamic nuclear polarization can suppress Zeeman gradients in double quantum dots, using electric dipole spin resonance measurements and a theoretical feedback model.

Contribution

It introduces a model showing nuclear polarization can compensate Zeeman gradients, leading to stabilized nuclear states in quantum dot systems.

Findings

Nuclear polarization reduces Zeeman gradient in quantum dots.

Resonance shifts indicate different nuclear polarization states.

Theoretical model predicts fixed points in nuclear polarization.

Abstract

We use electric dipole spin resonance to measure dynamic nuclear polarization in InAs nanowire quantum dots. The resonance shifts in frequency when the system transitions between metastable high and low current states, indicating the presence of nuclear polarization. We propose that the low and the high current states correspond to different total Zeeman energy gradients between the two quantum dots. In the low current state, dynamic nuclear polarization efficiently compensates the Zeeman gradient due to the $g$-factor mismatch, resulting in a suppressed total Zeeman gradient. We present a theoretical model of electron-nuclear feedback that demonstrates a fixed point in nuclear polarization for nearly equal Zeeman splittings in the two dots and predicts a narrowed hyperfine gradient distribution.