Information dynamics in a model with Hilbert space fragmentation

The fully frustrated ladder - a quasi-1D geometrically spin one half Heisenberg model is non-integrable with local conserved quantities on rungs of the ladder, inducing fragmentation Hilbert space into sectors composed singlets and triplets rungs. We explore far-from-equilibrium dynamics this through entanglement entropy out-of-time-ordered correlators (OTOC). post-quench highly anomalous as it shows clear non-damped revivals that emerge from short connected chunks whose persistence therefore consequence fragmentation. find maximum value follows picture where coherences between different fragments co-exist perfect thermalization within each fragment. This means eigenstate hypothesis holds all sufficiently large fragments. OTOC distance oscillations arising coupled fragments, which become decoherent at longer distances, sub-ballistic spreading long exponential decay stemming an emergent length scale tied to