Geometric Stability Spectra of Dipolar Bose Gases in Tunable Optical Lattices

TL;DR

This paper investigates how weak optical lattices affect the stability of dipolar Bose-Einstein condensates with roton-maxon dispersion, revealing geometry-dependent stability structures that can be used for spectroscopic roton detection.

Contribution

It introduces a detailed analysis of stability spectra in dipolar condensates under various lattice geometries and polarization tilts, highlighting mode matching as a key mechanism.

Findings

Stability depends strongly on lattice geometry and polarization tilt.

Rich stability structures emerge, similar to spectroscopic signatures.

Stability diagrams can be used to measure rotons spectroscopically.

Abstract

We examine the stability of quasi-two-dimensional dipolar Bose-Einstein condensates in the presence of weak optical lattices of various geometries. We find that when the condensate possesses a roton-maxon quasiparticle dispersion, the conditions for stability exhibit a strong dependence both on the lattice geometry and the polarization tilt. This results in rich structures in the system's stability diagram akin to spectroscopic signatures. We show how these structures originate from the mode matching of rotons to the perturbing lattice. In the case of a one-dimensional lattice, some of the features emerge only when the polarization axis is tilted into the plane of the condensate. Our results suggest that the stability diagram may be used as a novel means to spectroscopically measure rotons in dipolar condensates.