Diffusive and subdiffusive spin transport in the ergodic phase of a many-body localizable system

Understand

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.