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 experiments provide quantitative evidence that a dramatic enhancement of nuclear-spin diffusion from the GaAs quantum wells into the AlGaAs barriers is responsible for the recently reported sharp peak in the temperature dependence of heat capacity near v = 1. We discuss the physical origin of this behavior in terms of the possible Skyrme solid-liquid phase transition.