Spin transport in long-range interacting one-dimensional chain

We numerically study spin transport and nonequilibrium spin-density profiles in a clean onedimensional spin-chain with long-range interactions, decaying as a power-law, r-α with distance. We find two distinct regimes of transport: For α < 1=2, spin excitations relax instantaneously in the thermodynamic limit, and for α > 1=2, spin transport combines both diffusive and superdiffusive features. We show that while for α> 3=2 the spin diffusion coefficient is finite, transport in the system is never strictly diffusive, contrary to corresponding classical systems.