Interaction-induced weakening of localization in few-particle disordered Heisenberg chains

Abstract

We investigate real-space localization in the few-particle regime of the XXZ spin-1/2 chain with a random magnetic field. Our investigation focuses on the time evolution of the spatial variance of nonequilibrium densities, as resulting for a specific class of initial states, namely, pure product states of densely packed particles. Varying the strength of both particle-particle interactions and disorder, we numerically calculate the long-time evolution of the spatial variance s(t). For the two-particle case, the saturation of this variance yields an increased but finite localization length, with a parameter scaling different to known results for bosons. We find that this interaction-induced increase is stronger the more particles are taken into account in the initial condition. We further find that our nonequilibrium dynamics are clearly inconsistent with normal diffusion and instead point to subdiffusive dynamics with sigma(t) proportional to t(1/4).