Evidence for Skyrmion Crystallization from NMR Relaxation Experiments

Abstract

A resistively detected NMR technique was used to probe the two-dimensional electron gas in a $\mathrm{GaAs}/\mathrm{AlGaAs}$ quantum well. The spin-lattice relaxation rate $(1/T_1)$ was extracted at near complete filling of the first Landau level by electrons. The nuclear spin of ${}^{75}\mathrm{As}$ is found to relax much more efficiently with $T\to 0$ and when a well developed quantum Hall state with $R_{xx}\simeq 0$ occurs. The data show a remarkable correlation between the nuclear spin relaxation and localization. This suggests that the magnetic ground state near complete filling of the first Landau level may contain a lattice of topological spin texture, i.e., a Skyrmion crystal.