Boundary conformal field theory and symmetry-protected topological phases in 2+1 dimensions
Journal
Physical Review B
Journal Volume
96
Journal Issue
12
Date Issued
2017
Author(s)
Abstract
We propose a diagnostic tool for detecting nontrivial symmetry-protected topological (SPT) phases protected by a symmetry group G in 2+1 dimensions. Our method is based on directly studying the 1+1-dimensional anomalous edge conformal field theory (CFT) of SPT phases. We claim that if the CFT is the edge theory of an SPT phase, then there must be an obstruction to cutting it open. This obstruction manifests as the in-existence of boundary states in the CFT that preserves both the conformal symmetry and the global symmetry G. We discuss the relation between edgeability, i.e., the ability to find a consistent boundary state, and gappability, i.e., the ability to gap out a CFT, in the presence of G. We study several cases including time-reversal symmetric topological insulators, ZN symmetric bosonic SPT phases, and Z2×Z2 symmetric topological superconductors. © 2017 American Physical Society.
Subjects
Boundary state; Conformal field theories; Conformal symmetry; Diagnostic tools; Global symmetries; Symmetry groups; Time reversal; Topological phasis; Topology
Publisher
American Physical Society
Type
journal article