Many-body delocalization via symmetry emergence

N. S. Srivatsa; Roderich Moessner; Anne E. B. Nielsen

doi:10.1103/physrevlett.125.240401

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arXiv · 2002.07824

Many-body delocalization via symmetry emergence

N. S. Srivatsa·Roderich Moessner·Anne E. B. Nielsen

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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 $\Z_2$ 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.

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N. S. Srivatsa, Roderich Moessner, Anne E. B. Nielsen. 2020-02-18. Many-body delocalization via symmetry emergence. https://doi.org/10.1103/physrevlett.125.240401

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