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Integrability and quantum chaos in spin glass shards

The idias developed above for interaction induced thermalisation in finite Fermi systems were applied to quantum spin glass shards [99]. The studies are done for spin glass clusters (``shards") in a random transverse magnetic field. All spins are coupled so that at zero magnetic field the system represents the classical Sherrington-Kirkpatrick spin glass model. It is shown that for a weak or strong tranverse magnetic field the dynamics remains integrable and the level spacing statistics is Poissonian. The regime where quantum chaos and random matrix level statistics emerge from the integrable limits of weak and strong field is determined. Relations with quantum phase transitions are also analyzed [99].