Nuclear spin-lattice relaxation in p-type GaAs

TL;DR

This study measures the nuclear spin-lattice relaxation time in p-type GaAs using a novel optical method, revealing significantly faster relaxation than in n-type GaAs and explaining it through quadrupole relaxation mechanisms.

Contribution

It introduces a new experimental protocol to measure nuclear spin relaxation in the dark and provides a theoretical model explaining the rapid relaxation in p-GaAs.

Findings

T1 in p-GaAs is in the sub-second range.

T1 is much shorter than in n-GaAs.

Quadrupole relaxation explains the behavior.

Abstract

Spin-lattice relaxation of the nuclear spin system in p-type GaAs is studied using a three-stage experimental protocol including optical pumping and measuring the difference of the nuclear spin polarization before and after a dark interval of variable length. This method allows us to measure the spin-lattice relaxation time $T_1$ of optically pumped nuclei "in the dark", that is, in the absence of illumination. The measured $T_1$ values fall into the sub-second time range, being three orders of magnitude shorter than in earlier studied n-type GaAs. The drastic difference is further emphasized by magnetic-field and temperature dependences of $T_1$ in p-GaAs, showing no similarity to those in n-GaAs. This unexpected behavior is explained within a developed theoretical model involving quadrupole relaxation of nuclear spins, which is induced by electric fields within closely spaced donor-acceptor pairs.