Breakdown of the Korringa Law of Nuclear Spin Relaxation in Metallic GaAs

TL;DR

This study measures nuclear spin relaxation in GaAs epilayers, revealing deviations from the Korringa law and uncovering a sub-linear temperature dependence of relaxation rates in metallic GaAs.

Contribution

It introduces a new electrical pump-probe technique for measuring nuclear spin relaxation and demonstrates deviations from the Korringa law in metallic GaAs.

Findings

Nuclear spin relaxation times agree with NMR data for T > 1 K.

Relaxation rate follows a T^0.6 dependence between 0.1 K and 10 K.

Deviations from the expected Korringa law are observed.

Abstract

We present nuclear spin relaxation measurements in GaAs epilayers using a new pump-probe technique in all-electrical, lateral spin-valve devices. The measured T1 times agree very well with NMR data available for T > 1 K. However, the nuclear spin relaxation rate clearly deviates from the well-established Korringa law expected in metallic samples and follows a sub-linear temperature dependence 1/T1 ~ T^0.6 for 0.1 K < T < 10 K. Further, we investigate nuclear spin inhomogeneities.