2019/04/01 by Sarang Gopalakrishnan, Romain Vasseur, Brayden Ware · 1 citation
Physics and Astronomy · #cond-mat.quant-gas #cond-mat.stat-mech #cond-mat.str-el #quant-ph
paper · pdf · doi:10.1073/pnas.1906914116
published as PNAS 116 (33)16250-16255 (2019) · 7pp, 2 figures, plus 4pp. supplemental material
arxiv created 2019/04/01 · arxiv updated 2019/08/21
We compute the spin structure factor of XXZ spin chains in the Heisenberg and gapped (Ising) regimes in the high-temperature limit for nonzero magnetization, within the framework of generalized hydrodynamics including diffusive corrections. The structure factor shows a hierarchy of timescales in the gapped phase, owing to s-spin magnon bound states (`strings') of various sizes. Although short strings move ballistically, long strings move primarily diffusively as a result of their collisions with short strings. The interplay between these effects gives rise to anomalous power-law decay of the spin structure factor, with continuously varying exponents, at any fixed separation in the late-time limit. We elucidate the crossover to diffusion (in the gapped phase) and to superdiffusion (at the isotropic point) in the half-filling limit. We verify our results via extensive matrix product operator calculations.