Non-equilibrium dynamics in coupled bilayer two-dimensional bose gases

Thesis

Non-equilibrium (NEQ) many-body dynamics are ubiquitous, ranging from glassy systems to the emergence of structure in the early universe. Ultracold atomic gases provide an ideal, highly controllable platform for studying these phenomena, and this thesis presents a comprehensive investigation into the NEQ dynamics of coupled bilayer two-dimensional (2D) Bose gases.

In this thesis, we numerically investigate Josephson effects in bilayer 2D superfluids using classical-field simulations. We show that the system exhibits damped Josephson oscillations and macroscopic quantum self-trapping, and we discuss the associated excitations that emerge in the system. We then experimentally study the phase-ordering dynamics following a coupling quench that drives the system from a disordered to an ordered phase, realized using a well-controlled multiple-radio-frequency (MRF) dressed double-well potential. The resulting NEQ dynamics are probed using matter-wave interferometry, which provides direct access to correlation functions and vortex excitations of the relative-phase mode. Our results demonstrate that the system undergoes universal dynamics in the form of diffusion-type coarsening, in excellent agreement with classical-field numerical simulations.

This work broadens the understanding of NEQ and universal dynamics, and the methods presented here serve as a novel and highly tunable approach for exploring a wide range of NEQ dynamics.

Authors: Chang, E

• DOI: 10.5287/ora-gp5ag8mzd
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: two-dimensional Bose gases.; Josephson dynamics; universal dynamics; Non-equilibrium dynamics
• Subjects: Physics