Inhomogeneous Nuclear Spin Flips

TL;DR

This paper investigates how feedback between electronic states and nuclear spins in double quantum dots influences nuclear spin dynamics, showing that material properties and external magnetic fields determine whether nuclear spins equilibrate or diverge.

Contribution

It introduces a detailed analysis of feedback mechanisms affecting nuclear spin polarization in double quantum dots, highlighting the role of material parameters and magnetic fields.

Findings

Feedback can cause nuclear spins to either equilibrate or diverge.

The effect's strength depends on the material's g-factor and Overhauser coupling constant.

Lower external magnetic fields enhance the feedback effect.

Abstract

We discuss a feedback mechanism between electronic states in a double quantum dot and the underlying nuclear spin bath. We analyze two pumping cycles for which this feedback provides a force for the Overhauser fields of the two dots to either equilibrate or diverge. Which of these effects is favored depends on the g-factor and Overhauser coupling constant A of the material. The strength of the effect increases with A/V_x, where V_x is the exchange matrix element, and also increases as the external magnetic field B_{ext} decreases.