Many-body delocalization via symmetry emergence

Abstract

Many-body localization (MBL) provides a mechanism to avoid thermalization in many-body quantum systems. Here, we show that an {\it emergent} symmetry can protect a state from MBL. Specifically, we propose a ${\mathbb{Z}}_2$ symmetric model with nonlocal interactions, which has an analytically known, SU(2) invariant, critical ground state. At large disorder strength all states at finite energy density are in a glassy MBL phase, while the lowest energy states are not. These do, however, localize when a perturbation destroys the emergent SU(2) symmetry. The model also provides an example of MBL in the presence of nonlocal, disordered interactions that are more structured than a power law. The presented ideas raise the possibility of an `inverted quantum scar', in which a state that does not exhibit area law entanglement is embedded in an MBL spectrum, which does.

arXiv comment5 pages, 3 figures

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Cited by in corpus (9)

• Quantum Many-Body Scars: A Quasiparticle Perspective
• Floquet Prethermal Phase Protected by U(1) Symmetry on a Superconducting Quantum Processor
• Mobility edges through inverted quantum many-body scarring
• Tower of quantum scars in a partially many-body localized system
• Absence of localization in interacting spin chains with a discrete symmetry
• Tower of two-dimensional scar states in a localized system
• Escaping many-body localization in an exact eigenstate
• Universal Freezing Transitions of Dipole-Conserving Chains
• Delocalization in a partially disordered interacting many-body system