Nuclear spin relaxation in n-GaAs: from insulating to metallic regime

TL;DR

This study investigates nuclear spin relaxation in n-GaAs across insulating and metallic regimes, revealing enhanced relaxation at low magnetic fields likely due to quadrupole interactions influenced by electron localization and strain effects.

Contribution

It demonstrates the role of quadrupole interactions and strain in nuclear spin relaxation across different electron density regimes in n-GaAs.

Findings

Enhanced nuclear spin relaxation at low magnetic fields in both regimes.

Quadrupole interactions likely drive low-field relaxation.

Strain effects in microcavities amplify dipole-dipole interactions.

Abstract

Nuclear spin relaxation is studied in n-GaAs thick layers and microcavity samples with different electron densities. We reveal that both in metallic samples where electrons are free and mobile, and in insulating samples, where electrons are localized, nuclear spin relaxation is strongly enhanced at low magnetic field. The origin of this effect could reside in the quadrupole interaction between nuclei and fluctuating electron charges, that has been proposed to drive nuclear spin dynamics at low magnetic fields in the insulating samples. The characteristic values of these magnetic fields are given by dipole-dipole interaction between nuclei in bulk samples, and are greatly enhanced in microcavities, presumably due to additional strain, inherent to micro and nanostructures.