Investigations in vortex molecule dynamics and ring current generation in Bose-Einstein condensates : a dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University, Albany, New Zealand
Loading...
Date
2023
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
Topological excitations are a special type of long-lived excitation that are impervious
to small perturbations in cold atom systems. This thesis aims to investigate properties
of two different topological excitations in two-dimensional condensates using the Gross Pitaevskii equations (GPE).
The majority of this thesis investigates the dynamics of a vortex molecule in
coherently coupled Bose-Einstein condensates in different trap geometries. A vortex
molecule consists of two vortices in separate condensates bound together by a Josephson
vortex (also called a domain wall). We aim to shed light on vortex molecule dynamics
using a simple point-vortex framework. Firstly, we extend the point vortex framework to
account for the domain wall using a parametrized interaction energy. The interaction
energy is parametrized in special boundary conditions that emulate an infinite plane.
We then use this extended point vortex model to investigate the phase space and the
dynamics of a vortex molecule in a flat-bottomed channel trap. Our extended model
captures all the essential features of the phase space and agrees with GPE simulations of
a vortex molecule in a trap. We then expand the point vortex framework further to
account for the effect of the boundaries on the Josephson vortex by using a distributed
vorticity model. We use this continuous vorticity model to investigate the precession
frequency of a vortex molecule in an isotropic disc and find support for our model.
Additionally, we investigate a protocol to create persistent supercurrents in a ring
shaped single condensate. Though this protocol has been showed to adiabatically create
ring currents in ideal one-dimensional rings by Fialko et.al. [Phys. Rev. Lett. 108,
250402 (2012)], we use this protocol for two-dimensional rings and find the emergence of
ring currents non-adiabatically.
Description
Keywords
Bose-Einstein condensation, Condensed matter, Vortex-motion, Molecules