Effect of anisotropy on the entanglement of quantum states in a spin chain

The effect of the anisotropy of the interaction of a spin chain in the XXZ Heisenberg model on the concurrence of the states of neighboring sites is studied. When anisotropy increases, the maximum concurrence in a magnetic field increases above the value reached in the absence of the field. The maximum magnetic field allowing entanglement is linearly related to the anisotropy parameter.