Nuclear spin warm-up in bulk n-GaAs

TL;DR

This paper demonstrates that nuclear spin relaxation in bulk n-GaAs is significantly accelerated at low magnetic fields due to quadrupole relaxation caused by fluctuating donor charges, revealing a new relaxation mechanism.

Contribution

It identifies quadrupole relaxation as a key factor in low-field nuclear spin relaxation in bulk n-GaAs, previously thought to be negligible without optical pumping.

Findings

Spin-lattice relaxation accelerates at low magnetic fields

Quadrupole relaxation is induced by fluctuating donor charges

Bulk n-GaAs can be used to study quadrupole relaxation mechanisms

Abstract

We show that the spin-lattice relaxation in n-type insulating GaAs is dramatically accelerated at low magnetic fields. The origin of this effect, that cannot be explained in terms of well-known diffusion-limited hyperfine relaxation, is found in the quadrupole relaxation, induced by fluctuating donor charges. Therefore, quadrupole relaxation, that governs low field nuclear spin relaxation in semiconductor quantum dots, but was so far supposed to be harmless to bulk nuclei spins in the absence of optical pumping can be studied and harnessed in much simpler model environment of n-GaAs bulk crystal.