Depletion and fluctuations of a trapped dipolar Bose-Einstein condensate in the roton regime

TL;DR

This paper investigates the behavior of a trapped dipolar Bose-Einstein condensate in the roton regime, revealing characteristic peaks in non-condensate density and enhanced fluctuations linked to roton excitations.

Contribution

It provides new insights into the non-condensate density and fluctuations in dipolar BECs near the roton instability, including momentum space features.

Findings

Peak in non-condensate density at trap center due to rotons

Anomalous density becomes positive and peaked in the roton regime

Presence of a small momentum halo associated with roton excitations

Abstract

We consider the non-condensate density and density fluctuations of a trapped dipolar Bose-Einstein condensate, focusing on the regime where a roton-like excitation spectrum develops. Our results show that a characteristic peak in the non-condensate density occurs at trap center due to the rotons. In this regime we also find that the anomalous density becomes positive and peaked, giving rise to enhanced density fluctuations. We calculate the non-condensate density in momentum space and show that a small momentum halo is associated with the roton excitations.