title: Diffusive and Subdiffusive Spin Transport in the Ergodic Phase of a Many-Body Localizable System.
abstract: We study high temperature spin transport in a disordered Heisenberg chain in the ergodic regime. By employing a density matrix renormalization group technique for the study of the stationary states of the boundary-driven Lindblad equation we are able to study extremely large systems (400 spins). We find both a diffusive and a subdiffusive phase depending on the strength of the disorder and on the anisotropy parameter of the Heisenberg chain. Studying finite-size effects, we show numerically and theoretically that a very large crossover length exists that controls the passage of a clean-system dominated dynamics to one observed in the thermodynamic limit. Such a large length scale, being larger than the sizes studied before, explains previous conflicting results. We also predict spatial profiles of magnetization in steady states of generic nondiffusive systems.
authors: Physics Department, Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana, Slovenia.
authors: Marko
authors: M
authors: Žnidarič
authors: Abdus Salam ICTP, Strada Costiera 11, 34151 Trieste, Italy.|INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste, Italy.
authors: Antonello
authors: A
authors: Scardicchio
authors: Abdus Salam ICTP, Strada Costiera 11, 34151 Trieste, Italy.
authors: Vipin Kerala
authors: VK
authors: Varma