Entanglement across extended random defects in the XX spin chain

Abstract

We study the half-chain entanglement entropy in the ground state of the spin-1/2 XX chain across an extended random defect, where the strength of disorder decays with the distance from the interface algebraically as . In the whole regime , the average entanglement entropy is found to increase logarithmically with the system size L as , where the effective central charge depends on κ. In the regime , where the extended defect is a relevant perturbation, the strong-disorder renormalization group method gives , while, in the regime , where the extended defect is irrelevant in the bulk, numerical results indicate a non-zero effective central charge, which increases with κ. The variation of is thus found to be non-monotonic and discontinuous at .