Disorder-enhanced nuclear spin relaxation at Landau level filling factor one**Project supported by the National Basic Research Program of China (Grant Nos. 2012CB921703 and 2015CB921102), the National Natural Science Foundation of China (Grant Nos. 91121003, 11374337, and 61425015), the Chinese Academy of Sciences, the BMBF, and the German–Israel Foundation.

Abstract

The nuclear spin relaxation rate (1/T1) is measured for GaAs two-dimensional (2D) 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 ν = 1 in 1/T1 versus ν. Both the width and magnitude of the plateau increase with decreasing electron density. At low temperatures, 1/T1 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.