CRITICAL-BEHAVIOR OF NUCLEAR-SPIN DIFFUSION IN GAAS ALGAAS HETEROSTRUCTURES NEAR LANDAU-LEVEL FILLING NU=1/

Thermal measurements on a GaAs/AlGaAs heterostructure reveal that the state of the confined two-dimensional electrons profoundly affects the nuclear-spin diffusion near Landau level filling factor v = 1. The ex periments provide quantitative evidence that a dramatic enhancement of nuclear-spin diffusion from the GaAs quantum wells into the AlGaAs ba rriers is responsible for the recently reported sharp peak in the temp erature dependence of heat capacity near v = 1. We discuss the physica l origin of this behavior in terms of the possible Skyrme solid-liquid phase transition.