Spin squeezed states in two-dimensional antiferromagnet with a single impurity

We investigate the spin fluctuation in a two-dimensional antiferromagnet with a single impurity. The impurity plays the role of modulating the effective coupling between the spins. This system can realize the squeezed states under the alternate magnetic field like the perfect two-dimensional system. We calculate the 0-wavevector fluctuation of the spin system, and obtain the conditions of generating the squeezed states.