Vortex properties in the extended supersolid phase of dipolar Bose-Einstein condensates

TL;DR

This paper investigates vortex behavior in the supersolid phase of dipolar Bose-Einstein condensates, revealing that vortices are localized and exhibit unique dynamics due to the periodic potential, differing significantly from the superfluid phase.

Contribution

It provides the first detailed analysis of vortex properties and dynamics in the supersolid phase of dipolar BECs, highlighting vortex localization and energy transfer mechanisms.

Findings

Vortices in the supersolid phase are localized at interstitial sites.

Vortex dipoles in the supersolid phase approach each other via jumps, not continuous translation.

Vortex motion is hindered by an energy barrier due to the periodic potential.

Abstract

We study the properties of singly-quantized linear vortices in the supersolid phase of a dipolar Bose-Einstein condensate at zero temperature modeling $^{164}$Dy atoms. The system is extended in the $x-y$ plane and confined by a harmonic trap in the the polarization direction $z$. Our study is based on a generalized Gross-Pitaevskii equation. We characterize the ground state of the system in terms of spatial order and superfluid fraction and compare the properties of a single vortex and of a vortex dipole in the superfluid phase (SFP) and in the supersolid phase (SSP). At variance with a vortex in the SFP, which is free to move in the superfluid, a vortex in the SSP is localized at the interstitial sites and does not move freely. We have computed the energy barrier for motion from an equilibrium site to another. The fact that the vortex is submitted to a periodic potential has a dramatic effect on the dynamics of a vortex dipole made of two counter rotating parallel vortices; instead of rigidly translating as in the SFP, the vortex and anti-vortex approach each other by a series of jumps from one site to another until they annihilate in a very short time and their energy is transferred to bulk excitations.