Slow dynamics and nonergodicity of the bosonic quantum East model in the semiclassical limit.

Abstract

We study the unitary dynamics of the bosonic quantum East model, a kinetically constrained lattice model which generalizes the quantum East model to arbitrary occupation per site. We consider the semiclassical limit of large (but finite) site occupancy so that the dynamics is approximated by an evolution equation of the Gross-Pitaevskii kind. This allows us to numerically study in detail system sizes of hundreds of sites. Like in the spin-1/2 case, we find two dynamical phases, an active one of fast thermalization and an inactive one of slow relaxation and the absence of ergodicity on numerically accessible timescales. The location of this apparent ergodic to nonergodic transition coincides with the localization transition of the ground state. We further characterize states which are nonergodic on all timescales in the otherwise ergodic regime.