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Time glasses: Symmetry-broken chaotic phase with a finite gap

Taiki Haga*

  • *Contact author: taiki.haga@omu.ac.jp
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Phys. Rev. Research 8, 013257 – Published 9 March, 2026

DOI: https://doi.org/10.1103/v7x3-qvdl

Abstract

We introduce the time glass, a nonperiodic analog of the discrete time crystal that arises in periodically driven dissipative quantum many-body systems. This phase is defined by two key features: (1) spatial long-range order arising from the spontaneous breaking of an internal symmetry and (2) temporally chaotic oscillations of the order parameter, whose lifetime diverges with system size. In other words, a time glass is a state of matter in which all components evolve in a synchronized yet chaotic manner. To characterize the time glass phase, we focus on the spectral gap of the one-cycle (Floquet) Liouvillian, which determines the decay rate of the slowest relaxation mode. Theoretical arguments and numerical studies of periodically driven dissipative Ising models show that, in the time glass phase, the Liouvillian gap remains finite in the thermodynamic limit, in contrast to time crystals where the gap closes exponentially with system size. We further demonstrate that the Liouvillian gap converges to the decay rate of the order-parameter autocorrelation derived from the classical (mean-field) dynamics in the thermodynamic limit. This result establishes a direct correspondence between microscopic spectral features and emergent macroscopic dynamics in driven dissipative quantum systems. At first glance, the existence of a nonzero Liouvillian gap appears incompatible with the presence of indefinitely persistent chaotic oscillations. We resolve this apparent paradox by showing that the quantum Rényi divergence between a localized coherent initial state and the highly delocalized steady state grows unboundedly with system size. This divergence allows long-lived transients to persist even in the presence of a finite Liouvillian gap.

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Phys. Rev. Research 8, 013257– Published 9 March, 2026
  • Received 20 June 2025
  • Accepted 13 February 2026
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