Response of Bose gases in time-dependent optical superlattices

TL;DR

This paper investigates how ultracold Bose gases in one-dimensional optical superlattices respond dynamically to lattice modulation, revealing signatures of phase transitions and the effects of superlattice structures through numerical and analytical methods.

Contribution

It provides a detailed analysis of the dynamic response of Bose gases in superlattices, highlighting how excitation spectra change across different quantum phases, including the Mott-insulator and quasi Bose-glass phases.

Findings

Resonance positions and structures explain the superfluid to Mott-insulator transition.

Low-lying resonances indicate the presence of a quasi Bose-glass phase.

Spectral changes serve as experimental signatures for different quantum phases.

Abstract

The dynamic response of ultracold Bose gases in one-dimensional optical lattices and superlattices is investigated based on exact numerical time evolutions in the framework of the Bose-Hubbard model. The system is excited by a temporal amplitude modulation of the lattice potential, as it was done in recent experiments. For regular lattice potentials, the dynamic signatures of the superfluid to Mott-insulator transition are studied and the position and the fine-structure of the resonances is explained by a linear response analysis. Using direct simulations and the perturbative analysis it is shown that in the presence of a two-colour superlattice the excitation spectrum changes significantly when going from the homogeneous Mott-insulator the quasi Bose-glass phase. A characteristic and experimentally accessible signature for the quasi Bose-glass is the appearance of low-lying resonances and a suppression of the dominant resonance of the Mott-insulator phase.