Tunable entanglement of two-qubit XY model with in-plane magnetic fields

We study the thermal entanglement in the two-qubit XY model with magnetic fields in x-y plane. For the anisotropic XY model with uniform fields, we find that the entanglement of system exhibits different behaviors with the change of field directions at different field strength. For the isotropic XY model with nonuniform field, we find that the entanglement and limit temperature of system may be increased by tuning the relative angle between two local magnetic fields.