Anomalous Diffusion of Repulsive Bosons in a Two-Dimensional Random Potential

Two-dimensional (2D) bosons can undergo a Kosterlitz-Thouless transition[1], which does not involve macroscopic occupation of a single quantum state, but which can still result in superfluidity. In addition, strongly interacting bosons subject to a random potential can also exhibit superfluidity, as in the case of charged superfluidity that occurs in high-T c superconductors. Competition between the strength of the interaction and the degree of potential disorder are among the many complicated and competing factors which determine whether superfluidity is promoted or supressed in a Bose system[2]. Strong potential disorder forces bosons to localize and can result in an insulating Bose glass phase. Alternatively, repulsive interactions among bosons act to release them from their traps, to keep their inter-particle distances as uniform as the potential allows, and to arrange the flow direction. An appropriate interaction strength can thus promote superfluidity.