Аннотация
Many-body localization (MBL) provides a mechanism to avoid thermalization in
many-body quantum systems. Here, we show that an 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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