Hyperfine interaction dominated dynamics of nuclear spins in self-assembled quantum dots

TL;DR

This study investigates nuclear spin dynamics in self-assembled quantum dots, revealing two decay mechanisms and demonstrating prolonged coherence times, which advance understanding of quantum information storage in such systems.

Contribution

It identifies hyperfine-mediated intra-dot diffusion and co-tunneling processes as key decay mechanisms, and shows how to extend nuclear spin coherence times significantly.

Findings

Decay due to intra-dot diffusion lasts ~100 seconds

Gate voltage and temperature control extend decay time to ~30 hours

Hyperfine interactions dominate nuclear spin dynamics in quantum dots

Abstract

We measure the dynamics of nuclear spins in a self-assembled quantum dot at a magnetic field of 5 Tesla and identify two distinct mechanisms responsible for the decay of the Overhauser field. We attribute a temperature-independent decay which lasts ~100 seconds to intra-dot diffusion induced by hyperfine-mediated indirect nuclear spin interaction. In addition, we observe a gate-voltage and temperature dependent decay stemming from co-tunneling mediated nuclear spin flip processes. By adjusting the gate-voltage and lowering the electron temperature to ~200 milliKelvin, we prolong the corresponding decay time to ~30 hours. Our measurements indicate possibilities for exploring quantum dynamics of the central spin model using a single self-assembled quantum dot.