Multibranch Bogoliubov-Bloch spectrum of a cigar shaped Bose condensate in an optical lattice

TL;DR

This paper investigates the excitation spectrum of weakly coupled quasi-two-dimensional Bose condensates in an optical lattice, highlighting the importance of mode coupling and providing detailed spectra relevant for Bragg scattering experiments.

Contribution

It introduces a comprehensive hydrodynamic model including mode coupling to accurately describe the excitation spectrum of coupled Bose condensates.

Findings

Mode coupling significantly affects the excitation spectrum.

Complete spectra for axial quasiparticles with radial nodes are provided.

The spectrum can be experimentally observed via Bragg scattering.

Abstract

We study properties of excited states of an array of weakly coupled quasi-two-dimensional Bose condensates by using the hydrodynamic theory. The spectrum of the axial excited states strongly depends on the coupling among the various discrete radial modes in a given symmetry. By including mode-coupling within a given symmetry, the complete excitation spectrum of axial quasiparticles with various discrete radial nodes are presented. A single parameter which determines the strength of the mode coupling is identified. The excitation spectrum in the zero angular momentum sector can be observed by using the Bragg scattering experiments.