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  • Letter
  • Open Access

Stable infinite-temperature eigenstates in SU(2)-symmetric nonintegrable models

Christopher J. Turner1, Marcin Szyniszewski1,2,*, Bhaskar Mukherjee1,3, Ronald Melendrez4,5, Hitesh J. Changlani4,5, and Arijeet Pal1

  • *Contact author: mszynisz@gmail.com
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Phys. Rev. Research 8, L022064 – Published 30 June, 2026

DOI: https://doi.org/10.1103/rsm1-hzc3

Abstract

Nonintegrable many-body quantum systems typically thermalize at long times through the mechanism of quantum chaos. However, some exceptional systems, such as those harboring quantum scars, break thermalization, serving as testbeds for foundational problems of quantum statistical physics. Here, we investigate a class of nonintegrable bond-staggered models that is endowed with a large number of zero-energy eigenstates and possesses a non-Abelian internal symmetry. We use character theory to give a lower bound on the zero-energy degeneracy, which matches exact diagonalization results and is found to grow exponentially with the system size. We also show that few-magnon zero-energy states have an exact analytical description, allowing us to build a basis of low-entangled fixed-separation states, which is stable to most perturbations found in experiments. This remarkable dynamical stability of special states elucidates our understanding of nonequilibrium processes in non-Abelian chaotic quantum models.

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Phys. Rev. Research 8, L022064– Published 30 June, 2026
  • Received 11 October 2024
  • Accepted 29 April 2026
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