Experimental characterization of coherent magnetization transport in a one-dimensional spin system

We experimentally characterize the non-equilibrium, roomtemperature magnetization dynamics of a spin chain evolving under an effective double-quantum (DQ) Hamiltonian. We show that the Liouville space operators corresponding to the magnetization and the two-spin correlations evolve 90 degrees out of phase with each other, and drive the transport dynamics. For a nearest-neighbor-coupled N -spin chain, the dynamics are found to be restricted to a Liouville operator space whose dimension scales only as N 2, leading to a slow growth of multi-spin correlations. Even though long-range couplings are present in the real system, we find excellent agreement between the analytical predictions and our experimental results, confirming that leakage out of the restricted Liouville space is slow on the timescales investigated. Our results indicate that the group velocity of the magnetization is 6.04± 0.38μms−1, corresponding to a coherent transport over N ≈ 26 spins on the experimental timescale. As the DQ Hamiltonian is related to the standard one-dimensional 5 Author to whom any correspondence should be addressed. New Journal of Physics 13 (2011) 103015 1367-2630/11/103015+16$33.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft 2 XX Hamiltonian by a similarity transform, our results can be directly extended to XX quantum spin chains, which have been extensively studied in the context of both quantum magnetism and quantum information processing.