Stability and Excitations of a Dipolar Bose-Einstein Condensate with a Vortex

TL;DR

This paper investigates the stability of vortex states in dipolar Bose-Einstein Condensates, revealing how dipole interactions and trap geometry influence local collapse and vortex decay, which differ from contact-interaction BECs.

Contribution

It provides a detailed analysis of vortex stability in dipolar BECs, highlighting the effects of dipole interactions and trap shape on local collapse and vortex decay modes.

Findings

Singly-quantized vortices become unstable with increasing oblate trap aspect ratios.

Doubly-quantized vortices decay into two singly-quantized vortices under certain conditions.

Dipolar BECs exhibit local collapse and topological decay modes not present in contact-interaction BECs.

Abstract

We study the stability of singly- and doubly-quantized vortex states of harmonically trapped dipolar Bose-Einstein Condensates (BECs) by calculating the low-lying excitations of these condensates. We map the dynamical stability of these vortices as functions of the dipole-dipole interaction strength and trap geometry by finding where their excitations have purely real energy eigenvalues. In contrast to BECs with purely contact interactions, we find that dipolar BECs in singly-quantized vortex states go unstable to modes with an increasing number of angular and radial nodes for more oblate trap aspect ratios, corresponding to \emph{local} collapse that occurs on a characteristic length scale. Additionally, we find that dipolar BECs in doubly-quantized vortex states are unstable to decay into a different topological state (with two singly-quantized vortices) for all interaction strengths when the trap geometry is sufficiently prolate to make the dipoles attractive, and in windows of interaction strength when the trap geometry is sufficiently oblate to make the dipoles repulsive.