Bulk-boundary correspondence for intrinsically-gapless SPTs from group cohomology

• URL: http://arxiv.org/abs/2208.09001v2
• Date: Wed, 11 Jan 2023 17:24:30 GMT
• Title: Bulk-boundary correspondence for intrinsically-gapless SPTs from group cohomology
• Authors: Rui Wen, Andrew C. Potter
• Abstract summary: Intrinsically gapless symmetry protected topological phases (igSPT) are gapless systems with SPT edge states. An anomaly in the low-energy (IR) symmetry group emerges from an extended anomaly-free microscopic (UV) symmetry. In two- and three-dimensional systems, an additional possibility is that the emergent anomaly can be satisfied by an anomalous symmetry-enriched topological order.
• Score: 3.299672391663527
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Intrinsically gapless symmetry protected topological phases (igSPT) are gapless systems with SPT edge states with properties that could not arise in a gapped system with the same symmetry and dimensionality. igSPT states arise from gapless systems in which an anomaly in the low-energy (IR) symmetry group emerges from an extended anomaly-free microscopic (UV) symmetry We construct a general framework for constructing lattice models for igSPT phases with emergent anomalies classified by group cohomology, and establish a direct connection between the emergent anomaly, group-extension, and topological edge states by gauging the extending symmetry. In many examples, the edge-state protection has a physically transparent mechanism: the extending UV symmetry operations pump lower dimensional SPTs onto the igSPT edge, tuning the edge to a (multi)critical point between different SPTs protected by the IR symmetry. In two- and three- dimensional systems, an additional possibility is that the emergent anomaly can be satisfied by an anomalous symmetry-enriched topological order, which we call a quotient-symmetry enriched topological order (QSET) that is sharply distinguished from the non-anomalous UV SETs by an edge phase transition. We construct exactly solvable lattice models with QSET order.

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