Excitations, Rotational Dynamics, and Rotational Sensing in 2-Species Bose-Einstein Condensates

Lead Research Organisation: Newcastle University
Department Name: Mathematics and Statistics

Abstract

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.
 
Description We have developed analytically, and tested computationally, a new state-of-the-art method for modelling mixtures of very cold atomic gases, that could potentially lead to rotational sensors in the future.

More specifically, we have developed high-level numerical code to describe such systems and applied it in detail at equilibrium, focussing on the relative importance of different collisional rates. We have also implemented the full dynamical theory numerically, extending significantly beyond existing method: more specifically, in the context we have studied collective modes and thermalisation of two-component condensates, also providing a more accurate criterion of phase separation in an inhomogeneous potential. We have also used our new framework to critically re-assess the analysis of a range of experiments conducted over the past 2 decades, specifically demonstrating that the act of measuring the properties of a two-component mixture after expansion has to be used cautiously when trying to interpret the state of the system before expansion, as it is precisely the dynamics during expansion that leads to some of the observations. Our study has been supported by experimental evidence in full agreement with our work.

We have also recently characterised the expansion dynamics, and found good agreement with brand new experimental data (Aarhus group).

In the context of ring traps, we have investigated ring trap dynamics, focussing on the possiblity of generation of dark-solitonic structures, and also investigating the superflow past barriers, and have also succeded in implementing the ful dynamical (ZNG) code to two components on a ring.

More recently, we have also been studied the existence and stability of mixed and demixed modes in binary atomic Bose-Einstein condensates with repulsive interactions in a ring-trap geometry. The stability of such states is examined through eigenvalue spectra for small perturbations, produced by the Bogoliubov-de Gennes equations, and directly verified by simulations based on the coupled Gross-Pitaevskii equations, varying inter- and intra-species scattering lengths so as to probe the entire range of miscibility-immiscibility transitions.
Exploitation Route We have provided a new state of the art model for binary condensates at finite temperatures and recharacterised the phase miscibility profiles, also paying particular attention to expansion dynamics and its role in experimental observations. These findings are of direct relevance to any experimentalist working with multi-component mixtures, and the implications of our work, and the methodology developed, extends beyond the simple context of ultracold atoms. We have been pushing our ideas forward to other scientific communities, through the MultiSuper" network dealing with multicomponent superfluidity and superconductivity.
Sectors Education,Other
 
Description This project has provided a numerical framework for studying a number of experiments in numerous labs internationally, and has been used to assist in the analysis of experimental data by our collaborators at Aarhus (Prof. Jan Arlt's group), critically re-assessing how standard experiments of the last 2 decades are analysed (specifically the dynamical role of expansion imaging, a standard tool in ultracold atom experiments). The numerical expertise gained during this project is currently being used by the RA in the oil industry for surface modelling and interpretations.
Sector Aerospace, Defence and Marine,Education,Other
 
Description Aarhus University 
Organisation Aarhus University
Department Department of Physics and Astronomy
Country Denmark 
Sector Academic/University 
PI Contribution We have characterised the finite temperature equilibrium profiles and performed exploratory analysis of the dipole oscillations of two-component BECs in a harmonic trap. Our results indicate the interesting possibility to measure in-trap miscible-immiscibility transition by monitoring the damping rate of the dipole oscillations. Following the publication of a joint such work, we have more recently shown the crucial role of expansion imaging in phase-separation profiles. This work is to be submitted for publication as a joint experimental-theoretical paper soon.
Collaborator Contribution Experimental partners have been building up and testing their experimental setting, in parallel to our theoretical modelling of their experiment. More recently, they have confirmed by observations our theoretical findings about the density profiles after expansions imaging.
Impact Phase Separation and Dynamics of two-component Bose-Einstein condensates KL Lee, Nils B Jorgensen, I-K Liu, Lars Wackers, Jan Arlt, Nick P Proukakis Physical Review A 94 013602 (2016) and a follow-on paper about to be submitted soon.
Start Year 2015
 
Description Durham multi-component 
Organisation Durham University
Country United Kingdom 
Sector Academic/University 
PI Contribution We have derived a new approach to modelling multi-component atomic condensates at finite temperatures that supplements and extends existing theoretical treatments and is expected to be very sueful in modelling experiments (such as those done at Durham).
Collaborator Contribution They have been engaged in discussions about this new model, and also its interpretation. The intention is to test our new predictiojs against actualy experiments (at Durham, or elsewhere).
Impact There have been two joint research publications.
Start Year 2014
 
Description Durham multi-component 
Organisation Queen's University
Country Canada 
Sector Academic/University 
PI Contribution We have derived a new approach to modelling multi-component atomic condensates at finite temperatures that supplements and extends existing theoretical treatments and is expected to be very sueful in modelling experiments (such as those done at Durham).
Collaborator Contribution They have been engaged in discussions about this new model, and also its interpretation. The intention is to test our new predictiojs against actualy experiments (at Durham, or elsewhere).
Impact There have been two joint research publications.
Start Year 2014
 
Description Gary 2-Component 
Organisation National Changhua University of Education
Country Taiwan, Province of China 
Sector Academic/University 
PI Contribution We performed most numerical simulations and analysis fro two-component condensate oscilations.
Collaborator Contribution They helped with the characterization of some of the results, particularly by offering background insight into such systems.
Impact Phase Separation and Dynamics of two-component Bose-Einstein condensates KL Lee, Nils B Jorgensen, I-K Liu, Lars Wackers, Jan Arlt, Nick P Proukakis Physical Review A 94 013602 (2016) Stochastic growth dynamics and composite defects in quenched immiscible binary condensates I-K Liu, RW Pattinson, TP Billam, SA Gardiner, SL Cornish, T-M Huang, W-W Lin, S-C Gou, NG Parker, NP Proukakis Phys Rev A 93 023628 (2016)
Start Year 2014