Instanton effects in lattice models of bosonic symmetry-protected topological states
Luiz H. Santos, Eduardo Fradkin
Bosonic symmetry-protected topological (SPT) states are gapped disordered phases of matter possessing symmetry-preserving boundary excitations. It has been proposed that, at long wavelengths, the universal properties of an SPT system are captured by an effective nonlinear sigma model field theory in the presence of a quantized topological $\ensuremath{\theta}$ term. By studying lattice models of bosonic SPT states, we are able to identify, in their Euclidean path integral formulation, (discrete) Berry phases that hold relevant physical information on the nature of the SPT ground states. These discrete Berry phases are given intuitive physical interpretation in terms of instanton effects that capture the presence of a $\ensuremath{\theta}$ term on the microscopic scale.
arXiv:1512.06864•Physical review. B./Physical review. B•Apr 22, 2016•1 citation