Detecting edge degeneracy in interacting topological insulators through entanglement entropy

Understand

The existence of degenerate or gapless edge states is a characteristic feature of topological insulators, but is difficult to detect in the presence of interactons.

• We propose a new method to obtain the degeneracy of the edge states from the perspective of entanglement entropy, which is very useful to identify interacting topological states.
• Employing the determinant quantum Monte Carlo technique, we investigate the interaction effect on two representative models of fermionic topological insulators in one and two dimensions, respectively.
• In the two topologically nontrivial phases, the edge degeneracies are reduced by interactions but remain to be nontrivial.