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SYAD: Symposium SAMOP Dissertation Prize 2024

SYAD 1: SAMOP Dissertation Prize

SYAD 1.2: Invited Talk

Monday, March 11, 2024, 15:00–15:30, Paulussaal

Does a disordered Heisenberg quantum spin system thermalize? — •Titus Franz — Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany

Isolated quantum systems prepared far from equilibrium are generally expected to show thermalization. As a notable exception to this rule, strongly disordered systems can retain retrievable memory of their initial state for arbitrarily long times, leading to a rich phenomenology ranging from glassy dynamics to many-body localization. While exact numerical simulations are not possible beyond very small system sizes, we can experimentally probe the relaxation dynamics in an isolated spin system realized by a frozen gas of Rydberg atoms. Our findings reveal an anomalously slow dynamics that is independent of the specific type of Heisenberg Hamiltonian, suggesting a universal relaxation behavior. Furthermore, we observe characteristic features in the long-time magnetization as a function of a transverse external field, including non-analytic behavior at zero field. The emergence of these distinctive features seems incompatible with the assumption of local thermalization, which indicates that even large systems of thousands of spins with long-range interactions in three dimensions have not reached thermal equilibrium even at late times when the magnetization has already fully relaxed to zero. Both phenomena, the slow and universal relaxation dynamics and the absence of thermalization at late times, point toward the emergence of localization as the overarching principle governing out-of-equilibrium dynamics of spatially disordered quantum spin systems.

Keywords: Quantum Simulation; Rydberg Atoms; Thermalization; Disordered Quantum Spin Systems