Two-dimensional many-body-localized systems with an on-site abelian symmetry are shown to carry a topological index in the (generalized) third cohomology group of the symmetry group, robust to local perturbations.
Local Integrals of Motion for Topologically Ordered Many-Body Localized Systems
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abstract
Many-body localized (MBL) systems are often described using their local integrals of motion, which, for spin systems, are commonly assumed to be a local unitary transform of the set of on-site spin-z operators. We show that this assumption cannot hold for topologically ordered MBL systems. Using a suitable definition to capture such systems in any spatial dimension, we demonstrate a number of features, including that MBL topological order, if present: (i) is the same for all eigenstates; (ii) is robust in character against any perturbation preserving MBL; (iii) implies that on topologically nontrivial manifolds a complete set of integrals of motion must include nonlocal ones in the form of local-unitary-dressed noncontractible Wilson loops. Our approach is well suited for tensor-network methods, and is expected to allow these to resolve highly-excited finite-size-split topological eigenspaces despite their overlap in energy. We illustrate our approach on the disordered Kitaev chain, toric code, and X-cube model.
fields
cond-mat.dis-nn 1years
2019 1verdicts
CONDITIONAL 1representative citing papers
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Classification of symmetry-protected topological phases in two-dimensional many body-localized systems
Two-dimensional many-body-localized systems with an on-site abelian symmetry are shown to carry a topological index in the (generalized) third cohomology group of the symmetry group, robust to local perturbations.