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 Jz. The thermal entanglement at the fixed temperature can be enhanced when Jz increases. We strictly show that for any temperature T and Jz, the entanglement is symmetric with respect to zero inhomogeneous magnetic field, and the critical inhomogeneous magnetic field bc is independent of Jz. The critical magnetic field Bc increases with the increasing but the maximum entanglement value that the system can arrive at becomes smaller.