Quantum entanglement and pairing correlation in the reduced BCS pairing model

Using the particle–hole version of the density-matrix renormalization-group technique, the pairing correlation and the quantum entanglement of the reduced BCS pairing model are investigated. Both of them behave smoothly from the weak to the strong coupling regimes. A convergence radius (∼1/ln Ω) of condensation energy is detected by the first order derivative of the block–block entanglement. Furthermore, the block–block entanglement in the strong coupling regime shows distinct size dependence, and a logarithmic volume law is suggested numerically.

► Entanglement entropy of the reduced BCS model is investigated by PHDMRG technique.
► A convergence radius is detected by the first order derivative of entanglement entropy.
► Entanglement entropy is size dependent, and a logarithm volume law is suggested.