The Hallmarks of Superfluidity in Exotic Phases of Bose Gases : Self-bound Droplets, Mixed Bubbles and Supersolids
(2024)- Abstract
- This thesis investigates superfluidity in exotic phases of ultracold bosonic gases, namely self-bound droplets, mixed bubbles, and dipolar supersolids. We investigated these systems analytically and numerically using an extended Gross-Pitaevskii and Bogoliubov-de Gennes formalism. The dissertation offers six chapters, providing the necessary derivations to build the required background and understanding for the six papers this thesis comprises of:
In Paper I, we show that two-dimensional self-bound droplets in a bosonic mixture can support multiply singly-quantized vortices and give a protocol to create self-bound meta-stable persistent currents carrying vorticity.
Paper II studies the ground state properties of... (More) - This thesis investigates superfluidity in exotic phases of ultracold bosonic gases, namely self-bound droplets, mixed bubbles, and dipolar supersolids. We investigated these systems analytically and numerically using an extended Gross-Pitaevskii and Bogoliubov-de Gennes formalism. The dissertation offers six chapters, providing the necessary derivations to build the required background and understanding for the six papers this thesis comprises of:
In Paper I, we show that two-dimensional self-bound droplets in a bosonic mixture can support multiply singly-quantized vortices and give a protocol to create self-bound meta-stable persistent currents carrying vorticity.
Paper II studies the ground state properties of two-dimensional droplets via a super-Gaussian variational ansatz, showing excellent agreement with numerical solutions. Furthermore, we study whether the breathing mode is a feasible excitation in these droplets with and without vorticity.
In Paper III, we numerically demonstrate the existence of mixed bubbles near phase separation in a one-dimensional torus. These mixed bubbles coincide with a Higgs-Amplitude mode in the excitation spectrum. Additionally, we show that metastable persistent currents can occur, and the associated avoided level-crossing opens intriguing prospects for atomtronic concepts.
Paper IV investigates a dynamic stirring process in a toroidal dipolar supersolid with a weak link. The weak link couples two angular modes, allowing phase slips to occur under rotation. These phase slips induce a dynamic self-organizational process of continuous melting and re-freezing of crystal sites in the supersolid.
In Paper V, we demonstrate the existence of one-dimensional self-bound droplets in the few-body regime using exact diagonalization and compare these results to mean-field solutions. Across the transition from superfluid to self-bound droplet, we find the few-body precursor of a Higgs-Amplitude mode and observe a change in the rotational dispersion relation from negative curvature to parabolic.
Lastly, Paper VI investigates the decoupling of first sound, second sound, and Higgs-Amplitude mode across the superfluid-supersolid transition in a toroidal dipolar supersolid. These modes emerge from their elementary excitations, and we propose experimental protocols to probe these sound and amplitude modes selectively. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/f87b758b-8b43-4e71-a038-5d309d574a81
- author
- Stürmer, Philipp LU
- supervisor
- opponent
-
- Research Director Petrov, Dimitry, Universite Paris-Saclay, France.
- organization
- publishing date
- 2024-10-15
- type
- Thesis
- publication status
- published
- subject
- keywords
- Bose-Einstein condensation, Superfluidity, Supersolidity, Ultracold Atomic Gases, Dipolar Gases, Binary Bose Mixtures
- pages
- 179 pages
- publisher
- Department of Physics, Lund University
- defense location
- Lecture Hall Rydbergsalen, Department of Physics, Sölvegatan 14A, Faculty of Engineering LTH, Lund University, Lund.
- defense date
- 2024-11-08 09:15:00
- ISBN
- 978-91-8104-218-4
- 978-91-8104-217-7
- language
- English
- LU publication?
- yes
- id
- f87b758b-8b43-4e71-a038-5d309d574a81
- date added to LUP
- 2024-10-14 10:12:02
- date last changed
- 2024-10-16 10:26:47
@phdthesis{f87b758b-8b43-4e71-a038-5d309d574a81,
abstract = {{This thesis investigates superfluidity in exotic phases of ultracold bosonic gases, namely self-bound droplets, mixed bubbles, and dipolar supersolids. We investigated these systems analytically and numerically using an extended Gross-Pitaevskii and Bogoliubov-de Gennes formalism. The dissertation offers six chapters, providing the necessary derivations to build the required background and understanding for the six papers this thesis comprises of:<br/><br/>In Paper I, we show that two-dimensional self-bound droplets in a bosonic mixture can support multiply singly-quantized vortices and give a protocol to create self-bound meta-stable persistent currents carrying vorticity.<br/><br/>Paper II studies the ground state properties of two-dimensional droplets via a super-Gaussian variational ansatz, showing excellent agreement with numerical solutions. Furthermore, we study whether the breathing mode is a feasible excitation in these droplets with and without vorticity.<br/><br/>In Paper III, we numerically demonstrate the existence of mixed bubbles near phase separation in a one-dimensional torus. These mixed bubbles coincide with a Higgs-Amplitude mode in the excitation spectrum. Additionally, we show that metastable persistent currents can occur, and the associated avoided level-crossing opens intriguing prospects for atomtronic concepts.<br/><br/>Paper IV investigates a dynamic stirring process in a toroidal dipolar supersolid with a weak link. The weak link couples two angular modes, allowing phase slips to occur under rotation. These phase slips induce a dynamic self-organizational process of continuous melting and re-freezing of crystal sites in the supersolid.<br/><br/>In Paper V, we demonstrate the existence of one-dimensional self-bound droplets in the few-body regime using exact diagonalization and compare these results to mean-field solutions. Across the transition from superfluid to self-bound droplet, we find the few-body precursor of a Higgs-Amplitude mode and observe a change in the rotational dispersion relation from negative curvature to parabolic.<br/><br/>Lastly, Paper VI investigates the decoupling of first sound, second sound, and Higgs-Amplitude mode across the superfluid-supersolid transition in a toroidal dipolar supersolid. These modes emerge from their elementary excitations, and we propose experimental protocols to probe these sound and amplitude modes selectively.}},
author = {{Stürmer, Philipp}},
isbn = {{978-91-8104-218-4}},
keywords = {{Bose-Einstein condensation; Superfluidity; Supersolidity; Ultracold Atomic Gases; Dipolar Gases; Binary Bose Mixtures}},
language = {{eng}},
month = {{10}},
publisher = {{Department of Physics, Lund University}},
school = {{Lund University}},
title = {{The Hallmarks of Superfluidity in Exotic Phases of Bose Gases : Self-bound Droplets, Mixed Bubbles and Supersolids}},
url = {{https://lup.lub.lu.se/search/files/197379278/PhDThesis_Sturmer.pdf}},
year = {{2024}},
}