Nonlinear dynamics of quantum dot nuclear spins

TL;DR

This paper investigates the nonlinear behavior of nuclear spin polarization in quantum dots under magnetic fields, revealing hysteresis effects caused by feedback mechanisms between nuclear and electron spins.

Contribution

It introduces a semi-classical model that explains the observed hysteresis in nuclear spin polarization dynamics in quantum dots.

Findings

Hysteresis in Overhauser field as a function of magnetic field

Nonlinear dependence of nuclear spin polarization on external magnetic fields

Model successfully explains feedback-induced hysteresis

Abstract

We report manifestly nonlinear dependence of quantum dot nuclear spin polarization on applied magnetic fields. Resonant absorption and emission of circularly polarized radiation pumps the resident quantum dot electron spin, which in turn leads to nuclear spin polarization due to hyperfine interaction. We observe that the resulting Overhauser field exhibits hysteresis as a function of the external magnetic field. This hysteresis is a consequence of the feedback of the Overhauser field on the nuclear spin cooling rate. A semi-classical model describing the coupled nuclear and electron spin dynamics successfully explains the observed hysteresis but leaves open questions for the low field behaviour of the nuclear spin polarization.