Nonequilibrium Gross-Pitaevskii dynamics of boson lattice models

Abstract

Motivated by recent experiments on trapped ultracold bosonic atoms in an optical lattice potential, we consider the nonequilibrium dynamic properties of such bosonic systems for a number of experimentally relevant situations. When the number of bosons per lattice site is large, there is a wide parameter regime where the effective boson interactions are strong, but the ground state remains a superfluid (and not a Mott insulator): we describe the conditions under which the dynamics in this regime can be described by a discrete Gross-Pitaevskii equation. We describe the evolution of the phase coherence after the system is initially prepared in a Mott insulating state, and then allowed to evolve after a sudden change in parameters places it in a regime with a superfluid ground state. We also consider initial conditions with a “π phase” imprint on a superfluid ground state (i.e., the initial phases of neighboring wells differ by π), and discuss the subsequent appearance of the density wave order and “Schrödinger cat,” i.e., macroscopic quantum interference, states.