Nonequilibrium dynamics in Bose-Hubbard ladders

Motivated by a recent experiment on the nonequilibrium dynamics of interacting bosons in ladder-shaped optical lattices, we report exact calculations on the sweep dynamics of Bose-Hubbard systems in finite two-leg ladders. The sweep changes the energy bias between the legs linearly over a finite time. As in the experiment, we study the cases of (a) the bosons initially all in the lower-energy leg (ground-state sweep) and (b) the bosons initially all in the higher-energy leg (inverse sweep). The approach to adiabaticity in the inverse sweep is intricate, as the transfer of bosons is nonmonotonic as a function of both sweep time and intraleg tunnel coupling. Our exact study provides explanations for these nonmonotonicities based on features of the full spectrum, without appealing to concepts (e.g., gapless excitation spectrum) that are more appropriate for the thermodynamic limit. We also demonstrate and study Stuckelberg oscillations in the finite-size ladders. DOI: 10.1103/PhysRevA.86.063633