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arXiv · 2503.03801

Restoring thermalization in long-range quantum magnets with staggered magnetic fields

Lucas Winter·Pietro Brighi·Andreas Nunnenkamp
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Abstract

Quantum systems with strong long-range interactions are thought to resist thermalization because of their discrete energy spectra. We show that applying a staggered magnetic field to a strong long-range Heisenberg antiferromagnet restores thermalization for a large class of initial states by breaking permutational symmetry. Using self-consistent mean-field theory and exact diagonalization, we reveal that the energy spectrum, while composed of discrete subspaces, collectively forms a dense spectrum. The equilibration time is independent of system size and depends only on the fluctuations in the initial state. For initial states at low to intermediate energies, the long-time average aligns with the microcanonical ensemble. However, for states in the middle of the spectrum the long-time average depends on the initial state due to quantum scar-like eigenstates localized at unstable points in classical phase space. Our results can be readily tested on a range of experimental platforms, including Rydberg atoms or optical cavities.

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Lucas Winter, Pietro Brighi, Andreas Nunnenkamp. 2025-03-05. Restoring thermalization in long-range quantum magnets with staggered magnetic fields. https://arxiv.org/abs/2503.03801

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