Optically-patterned nuclear doughnuts in GaAs/MnAs heterostructures

TL;DR

This paper presents a method to optically pattern nuclear spin polarization in GaAs/MnAs heterostructures, revealing a unique annular 'doughnut'-shaped polarization structure using Kerr rotation microscopy.

Contribution

It introduces a novel optical patterning scheme for nuclear spins in semiconductor/ferromagnet heterostructures and visualizes the resulting non-trivial polarization pattern.

Findings

Nuclear polarization forms an annular structure with circular symmetry.

The pattern is a dip at the center, not a peak.

The method uses scanning time-resolved Kerr rotation microscopy.

Abstract

We demonstrate a scheme for optically patterning nuclear spin polarization in semiconductor/ferromagnet heterostructures. A scanning time-resolved Kerr rotation microscope is used to image the nuclear spin polarization that results when GaAs/MnAs epilayers are illuminated with a focused laser having a Gaussian profile. Rather than tracking the intensity profile of the laser spot, these images reveal that the nuclear polarization forms an annular lateral structure having circular symmetry with a dip rather than a peak at its center.