Fundamental Excitations of Nonconservative Quantum Fluids
type: CreativeWork
description: The study of Bose-Einstein condensates (BECs) has represented a core subject of physics for decades. Recently however, experiments have demonstrated a fundamentally distinct, inherently nonequilibriated class of BEC from photonic quasiparticles known as exciton-polaritons (polaritons). These photonic condensates are free to gain or lose energy as a part of their dynamics, and are thus not constrained to tend towards thermodynamic equilibrium. This greatly increases their pattern forming capabilities, but in turn severely complicates their theoretical treatment. The dynamical theory of these nonconservative condensates is an emerging field which resides at the intersection of the theories of nonequilibrium pattern formation, nonlinear wave dynamics and condensed matter theory. In this thesis I describe several contributions to this theory of $\textit{nonconservative}$ quantum hydrodynamics, and towards the argument that it truly represents a paradigmatic departure from the now mature theory of equilibrium quantum hydrodynamics. The polariton is formed in an optical cavity: cavity photons excite and superpose with excitons in a solid state sample to form bosonic light-matter quasiparticles. However, photons are trapped in the cavity for finite times, and are thus continually lost. A key characteristic of the polariton condensate is thus that to be created or sustained, they must be fed by an optical pump, which can take on any incident geometry, and which can be resonant or nonresonant with the natural frequency of the optical cavity. As a result, understanding the dynamical and structural implications of different forcing scenarios is fundamentally important for these systems, and exploring these scenarios is a major theme of this work. In the first part of the thesis I focus on the role of pumping geometry on the dynamical behaviours and structural forms that can emerge. First, I show that an annular pumping geometry can lead to the spontaneous formation of stable m…
abstract: The study of Bose-Einstein condensates (BECs) has represented a core subject of physics for decades. Recently however, experiments have demonstrated a fundamentally distinct, inherently nonequilibriated class of BEC from photonic quasiparticles known as exciton-polaritons (polaritons). These photonic condensates are free to gain or lose energy as a part of their dynamics, and are thus not constrained to tend towards thermodynamic equilibrium. This greatly increases their pattern forming capabilities, but in turn severely complicates their theoretical treatment. The dynamical theory of these nonconservative condensates is an emerging field which resides at the intersection of the theories of nonequilibrium pattern formation, nonlinear wave dynamics and condensed matter theory. In this thesis I describe several contributions to this theory of $\textit{nonconservative}$ quantum hydrodynamics, and towards the argument that it truly represents a paradigmatic departure from the now mature theory of equilibrium quantum hydrodynamics. The polariton is formed in an optical cavity: cavity photons excite and superpose with excitons in a solid state sample to form bosonic light-matter quasiparticles. However, photons are trapped in the cavity for finite times, and are thus continually lost. A key characteristic of the polariton condensate is thus that to be created or sustained, they must be fed by an optical pump, which can take on any incident geometry, and which can be resonant or nonresonant with the natural frequency of the optical cavity. As a result, understanding the dynamical and structural implications of different forcing scenarios is fundamentally important for these systems, and exploring these scenarios is a major theme of this work. In the first part of the thesis I focus on the role of pumping geometry on the dynamical behaviours and structural forms that can emerge. First, I show that an annular pumping geometry can lead to the spontaneous formation of stable m…
author: Alperin, Samuel
language: eng
keywords: Bose Einstein Condensate, Polariton, Pattern Formation, Nonequilibrium Physics, Complex Systems, Condensed Matter, Soliton, Quantum Fluids
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2021-06-22
date modified: 2026-07-22T22:24:24Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.86076