Negativity of Heisenberg XY Model
Siping Liu
Abstract
Using a universal entanglement measure,negativity,we investigate the thermal entanglement of two-qubit Heisenberg XY model in thermal equilibrium at temperature T in the presence of an external magnetic field B.When anisotropy parameter γ is large enough there occurs a revival of the entanglement.By adjusting the magnetic field B,one can produce entanglement for any finite T.For isotropic case there is no entanglement above a critical temperature that is independent of the external B field.