3:30–4:30 pm Maria Goeppert-Mayer Lecture Hall - KPTC 106
Landscapes of Quantum Thermalization and Non-Ergodic Dynamics
Maksym Serbyn,IST, Austria
In this colloquium, I will focus on out-of-equilibrium many-body quantum systems. In contrast to low-energy states, described through the notion of phases of matter, our understanding of out-of-equilibrium properties is in its infancy. A natural coarse classification comes from the approach to thermal equilibrium: generic systems thermalize in accordance with the eigenstate thermalization hypothesis, erasing local memory of their initial state. Yet striking exceptions exist. I will survey the landscape of quantum thermalization and the mechanisms of its failure. Many-body localization provides the paradigmatic strong ergodicity breaking, where disorder entirely arrests thermalization and preserves local memory. Quantum many-body scars offer a weaker violation, in which rare non-thermal eigenstates coexist with an otherwise thermalizing spectrum. I will also discuss how slow non-ergodic dynamics emerges near first-order quantum phase transitions. Beyond classification, these failures of thermalization enable genuinely new out-of-equilibrium phenomena, including discrete time crystals and coherent dynamical order. These phases have no equilibrium analog and are directly accessible in current quantum simulators. I will conclude by outlining a broader perspective in which non-ergodic points serve as organizing centers that structure the landscape of thermalization and its timescales.