Restoring thermalization in long-range quantum magnets with staggered magnetic fields
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.
Keywords
Cite
@article{arxiv.2503.03801,
title = {Restoring thermalization in long-range quantum magnets with staggered magnetic fields},
author = {Lucas Winter and Pietro Brighi and Andreas Nunnenkamp},
journal= {arXiv preprint arXiv:2503.03801},
year = {2025}
}