Deciphering the nonlocal entanglement entropy of fracton topological orders

The authors discuss a lower bound of nonlocal entanglement entropy (a generalization of topological entanglement entropy). The lower bound applies to Abelian conventional topological order as well as to type-I and type-II fracton models. It provides the physical intuition that each type of topological excitation, created by a deformable string, membrane, or fractal operator, gives a contribution to the nonlocal entanglement entropy. For fracton models, the lower bound is geometry dependent; it can take extensive values.