Disorder Enhanced Nuclear Spin Relaxation at Landau Level Filling Factor One

TL;DR

This study investigates how disorder influences nuclear spin relaxation in GaAs quantum Hall systems, revealing a disorder-induced plateau near filling factor 1 and a nontrivial relaxation mechanism involving inhomogeneities and skyrmions.

Contribution

It uncovers a disorder-enhanced nuclear spin relaxation mechanism and characterizes a tilted plateau feature near $ u=1$ in the quantum Hall regime.

Findings

Observation of a tilted plateau in 1/T₁ near ν=1

Plateau width and magnitude increase with decreasing electron density

Arrhenius temperature dependence with small energy gaps

Abstract

The nuclear spin relaxation rate (1/$T_1$) is measured for GaAs two-dimensional electron systems in the quantum Hall regime with an all-electrical technique for agitating and probing the nuclear spins. A "tilted plateau" feature is observed near the Landau level filling factor $\nu=1$ in 1/$T_1$ versus $\nu$. Both width and magnitude of the plateau increase with decreasing electron density. At low temperatures, 1/$T_1$ exhibits an Arrhenius temperature dependence within the tilted plateau regime. The extracted energy gaps are up to two orders of magnitude smaller than the corresponding charge transport gaps. These results point to a nontrivial mechanism for the disorder enhanced nuclear spin relaxation, in which microscopic inhomogeneities play a key role for the low energy spin excitations related to skyrmions.