Thermal entanglement in a two-qubit Heisenberg XXZ spin chain under an inhomogeneous magnetic field

The thermal entanglement in a two-qubit Heisenberg XXZ spin chain is investigated under an inhomogeneous magnetic field b. We show that the ground-state entanglement is independent of the interaction of z-component J_z. The thermal entanglement at the fixed temperature can be enhanced when J_z increases. We strictly show that for any temperature T and J_z, the entanglement is symmetric with respect to zero inhomogeneous magnetic field, and the critical inhomogeneous magnetic field b_c is independent of J_z. The critical magnetic field B_c increases with the increasing ∣b∣ but the maximum entanglement value that the system can arrive at becomes smaller.