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arXiv:2601.05627 · Physical review. B./Physical review. B

Chaos, thermalization and breakdown of quantum-classical correspondence in a collective many-body system

Ángel L. Corps, Sebastián Gómez, Pavel Stránský, Armando Relaño, Pavel Cejnar

quant-phcond-mat.stat-mechSubmitted Jan 9, 2026• Announced Jan 12, 2026• 0 citations
v1 · Jan 9, 2026v2 · Apr 23, 2026
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Abstract

We investigate thermalization and the quantum-classical correspondence in the fully-connected Bose-Hubbard model, focusing on the four-site case. Our analysis of the classical phase-space structure and its excited-state quantum phase transitions leads us to three dynamical regimes: symmetry-breaking low-energy states, an intermediate region where quantum and classical equilibrium states markedly disagree, and a high-energy regime with restored correspondence. The observed classical intermittency above the first excited-state quantum phase transition contrasts with quantum dynamics, which remains trapped in symmetry-breaking sectors despite the existence of a classically connected phase space. This mismatch originates from the population of imbalance-carrying eigenstates and persists even for relatively large number of particles. Our results reveal unexpectedly slow convergence to the classical limit, signaling robust finite-size effects in collective many-body dynamics.

Journal reference
Phys. Rev. B 113, 144315 (2026)
DOI
10.1103/vsyl-21mr
Comments
11 pages, 7 figures

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