Non-equilibrium dynamics in Bose-Hubbard ladders

TL;DR

This paper presents exact calculations of non-equilibrium dynamics in finite Bose-Hubbard ladders, revealing complex transfer behaviors and oscillations during energy bias sweeps, with insights into finite-size effects.

Contribution

It provides the first exact finite-size analysis of sweep dynamics in Bose-Hubbard ladders, explaining non-monotonic transfer and Stueckelberg oscillations without thermodynamic assumptions.

Findings

Non-monotonic boson transfer as a function of sweep time and coupling.

Identification of spectral features explaining transfer behaviors.

Observation of Stueckelberg oscillations in finite ladders.

Abstract

Motivated by a recent experiment on the non-equilibrium 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 non-monotonic as a function of both sweep time and intra-leg tunnel coupling. Our exact study provides explanations for these non-monotonicities 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 Stueckelberg oscillations in the finite-size ladders.