Burnett coefficients in quantum many-body systems

The Burnett coefficient B is investigated for transport in one-dimensional quantum many-body systems. Extensive numerical computations in spin-1/2 chains suggest a linear growth with time, B(t) similar to t, for nonintegrable chains exhibiting diffusive transport. For integrable spin chains in the metallic regime, on the other hand, we find a cubic growth with time, B(t) similar to -D(m)(2)t(3), with the proportionality constant being simply a square of the Drude weight D-m. The results are corroborated with additional studies in noninteracting quantum chains and in the classical limit of large-spin chains.