Universality and weak-ergodicity breaking in quantum quenches

Year: 2026

Authors: Giachetti G., Solfanelli A., Defenu N.

Autors Affiliation: Univ Paris Cite, Sorbonne Univ, CNRS, Lab Phys,Ecole Normale Super, F-75005 Paris, France; Univ Paris Cite, PSL Univ, Sorbonne Univ, F-75005 Paris, France; Max Planck Inst Phys Komplexer Syst, Nothnitzer Str 38, D-01187 Dresden, Germany; Swiss Fed Inst Technol, Inst Theoret Phys, Wolfgang-Pauli-Str 27, Zurich, Switzerland; CNR INO, Area Sci Pk, I-34149 Trieste, Italy.

Abstract: Understanding equilibration and universality after sudden quantum quenches remains a central challenge in isolated many-body systems. Persistent oscillations and anomalous scaling reported in lattice models appear to challenge the standard picture based on integrability and quantum-to-classical correspondence. Focusing on the quantum O(n) model in the large-n limit, we show that these apparent anomalies originate from lattice effects and an underlying integrable structure. In particular, we map the postquench dynamics onto an integrable Neumann system and we derive an exact action-angle description valid in the thermodynamic limit. This framework explains both the convergence of long-time averages to the generalized Gibbs ensemble and the emergence of persistent oscillations associated with an isolated mode at the upper edge of the phonon spectrum. We further show that the expected thermal universality class is recovered in the appropriate scaling regime, while the oscillations disappear in the quantum-field-theory limit.

Journal/Review: PHYSICAL REVIEW RESEARCH

Volume: 8 (4)      Pages from: 43026-1  to: 43026-13

More Information: G.G. acknowledges the support of the MSCA Grant No. 101152898 (DREAMS) . This research was funded by the Swiss National Science Foundation (SNSF) Grants No. 200021-207537 and No. 200021-236722, by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy EXC2181/1-390900948 (the Heidelberg STRUCTURES Excellence Cluster) , and by the European Union under Grant Agreement No. 101077500-QLRNet. Partial support by Grant No. NSF PHY-230935 to the Kavli Institute for Theoretical Physics (KITP) is also acknowledged.
KeyWords: Spherical Model; Systems
DOI: 10.1103/nh76-cb9q