The idea of equilibration is ubiquitous throughout nature. However, describing the out-of-equilibrium dynamics of an isolated system – be it caused by a disturbance and subsequent “rethermalisation”, or by passing through a phase transition – is both an intriguing and difficult question to answer.
Phase transitions occur throughout all the fields of science and across diverse physical systems, from the phase transition of water to ice, to the phase transitions that occurred in the early universe. Physical systems that appear completely unrelated on a microscopic level can be organized into universality classes that exhibit similar physics during the phase transition.
Phase transitions are usually investigated as equilibrium phenomena even though a second order phase transition experiences a critical slowing down and departs from equilibrium at the critical point, where the new broken symmetry phase is chosen. The description of this “choice” is at the heart of the famous Kibble-Zurek mechanism (KZM), which describes a possible mechanism for the formation of domain structures in the early universe. The subsequent merging of these spatial domains lead to the formation of defects like domain walls, monopoles, strings, and textures.
This project has two distinct directions:
(i) Quantum Equilibration: perturbing a quantum system (a BEC of metastable helium) and studying the equilibration process as a function of the system parameters (temperature, density, and dimensionality).
(ii) Exploring the Kibble-Zurek Mechanism: investigating the dynamic evolution of the system correlation length, when the second order phase transition associated with a metastable helium BEC is crossed at a finite rate.