{
  "id": "1912.06660",
  "version": "v1",
  "published": "2019-12-13T19:00:03.000Z",
  "updated": "2019-12-13T19:00:03.000Z",
  "title": "Strong ergodicity breaking due to local constraints in a quantum system",
  "authors": [
    "Sthitadhi Roy",
    "Achilleas Lazarides"
  ],
  "comment": "14 pages, 11 figures",
  "categories": [
    "cond-mat.dis-nn",
    "cond-mat.stat-mech",
    "cond-mat.str-el",
    "quant-ph"
  ],
  "abstract": "Quantum systems that violate the eigenstate thermalisation hypothesis thereby falling outside the paradigm of conventional statistical mechanics are of both intellectual and practical interest. We show that such a breaking of ergodicity may arise purely due to local constraints on random many-body Hamiltonians. As an example, we study an ergodic quantum spin-1/2 model which acquires a localised phase upon addition of East-type constraints. We establish its phenomenology using spectral and dynamical properties obtained by exact diagonalisation. Mapping the Hamiltonian to a disordered hopping problem on the Fock space graph we find that potentially non-resonant bottlenecks in the Fock-space dynamics, caused by spatially local segments of frozen spins, lie at the root of localisation. We support this picture by introducing and solving numerically a class of random matrix models that retain the bottlenecks. Finally, we obtain analytical insight into the origins of localisation using the forward-scattering approximation. A numerical treatment of the forward-scattering approximation yields critical points which agree quantitatively with the exact diagonalisation results.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-12-13T19:00:03.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "strong ergodicity breaking",
      "quantum system",
      "local constraints",
      "exact diagonalisation",
      "random matrix models"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 14,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}