Ergodicity and its deviation due to scarring phenomena in interacting quantum systems

Sinha, Sudip (2025) Ergodicity and its deviation due to scarring phenomena in interacting quantum systems. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Sudip Sinha (19RS063)) 19RS063.pdf - Submitted Version Restricted to Repository staff only Download (6MB)

Abstract

In recent years, the non-equilibrium dynamics of complex quantum systems have attracted significant attention, especially in the context of ergodicity and thermalization. However, despite the presence of complex interactions, there can be various factors that hinder thermalization and lead to deviation from ergodicity. The many-body quantum scar is one such phenomenon that generated significant impetus following its experimental observation in ultracold Rydberg atoms, where the memory of a specific choice of initial state is retained during the dynamics. In this thesis, we consider some examples of collective quantum models, such as the Bose-Josephson junction, to explore the classical route to ergodicity and elucidate the underlying classicality behind the formation of quantum scars in the presence of interactions. The added advantage of such systems is that they not only provide a classical-quantum correspondence as they possess a tunable semiclassical limit but they can also be realized experimentally in cold atoms, trapped ions, as well as circuit and cavity quantum electrodynamics setups. The key findings include the identification of eigenstates bearing the scar of the classically unstable dynamical steady states and periodic orbits, as well as the analysis of their characteristic features, which has also been extended to periodically driven systems. Importantly, we shed light on their connection with the underlying classicality, particularly through the entanglement properties and the dynamics of out-of-time-ordered correlators (OTOCs). Our results offer valuable insights into the formation of many-body quantum scars in complex quantum systems. Finally, we discuss the potential avenues of research on ergodicity and quantum scars that can be explored in the future.

Actions (login required)

View Item