Finite-Temperature Topological Invariant for Interacting Systems
Finite-Temperature Topological Invariant for Interacting Systems
We generalize the Ensemble Geometric Phase (EGP), recently introduced to classify the topology of density matrices, to finite-temperature states of interacting systems in one spatial dimension (1D). This includes cases where the gapped ground state has a fractional filling and is degenerate. At zero temperature the corresponding topological invariant agrees …