Exotic roton excitations in quadrupolar Bose-Einstein condensates

TL;DR

This paper explores the emergence of exotic roton excitations in a two-dimensional quadrupolar Bose-Einstein condensate, revealing complex minima structures and proposing experimental detection methods.

Contribution

It provides a comprehensive mapping of roton behaviors in quadrupolar BECs and suggests experimental approaches to observe these novel excitations.

Findings

Multiple roton minima depending on parameters

Identification of instability regions in parameter space

Proposal for experimental detection via density wave dynamics

Abstract

We investigate the occurrence of rotons in a quadrupolar Bose-Einstein condensate confined to two dimensions. Depending on the particle density, the ratio of the contact and quadrupole-quadrupole interactions, and the alignment of the quadrupole moments with respect to the confinement plane, the dispersion relation features two or four point-like roton minima, or one ring-shaped minimum. We map out the entire parameter space of the roton behavior and identify the instability regions. We propose to observe the exotic rotons by monitoring the characteristic density wave dynamics resulting from a short local perturbation, and discuss the possibilities to detect the predicted effects in state-of-the-art experiments with ultracold homonuclear molecules.