Topological entanglement entropy of interacting disordered zigzag graphene ribbons

Interacting disordered zigzag graphene nanoribbons have fractional charges, are quasi-one-dimensional, and display an exponentially small gap. Our numerical computations showed that the topological entanglement entropy of these systems has a finite but universal value, independent strength interaction disorder. The result was obtained for shows disorder-free phase is critical becomes unstable in presence