# SKM 2023 – wissenschaftliches Programm

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# DY: Fachverband Dynamik und Statistische Physik

## DY 49: Critical Phenomena and Phase Transitions

### DY 49.6: Vortrag

### Donnerstag, 30. März 2023, 16:30–16:45, ZEU 160

**Global Speed Limit for Finite-Time Dynamical Phase Transition in Nonequilibrium Relaxation** — •Kristian Blom and Aljaz Godec — Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany

The nearest-neighbor interacting Ising model is a paradigm for classical many-body physics. Recent works unraveled an intriguing finite-time dynamical phase transition in the thermal relaxation of a mean field Curie-Weiss Ising model. This phase transition reflects a sudden switch in the dynamics, and manifests as a cusp in the probability density of magnetization. Its existence in systems with a finite range of interaction, however, remained unclear.

Employing the Bethe-Guggenheim approximation, which is exact on Bethe lattices, we demonstrate the finite-time dynamical phase transition in nearest-neighbor Ising systems for arbitrary quenches, including those within the two-phase coexisting region. Strikingly, for any given initial condition we prove and explain the existence of non-trivial speed limits for the dynamical phase transition and the relaxation of magnetization, which are absent in the mean field setting. Pair correlations, which are neglected in mean field theory, and trivial in the Curie-Weiss model, account for kinetic constraints due to frustrated local configurations, that give rise to a global speed limit.

Our findings may be relevant for optimizing ultrafast optical-switching ferromagnetic materials.