Quasi-Spin Squeezed State for Lipkin Model
Y. Tsue, N. Azuma, Atsushi KURIYAMA, M. Yamamura · Progress of Theoretical Physics · 1996
To go beyond the usual Hartree-Fock approximation, a quasi-spin squeezed state is introduced in the Lipkin model. We define the quasi-spin squeezed state from the su(2)-coherent state in a manner similar to that for the ordinary boson squeezed state. In this paper, we deal only with the case that the parameters included in this state are time-independent. It is then seen that the exact energy eigenvalues of the ground state are reproduced with high accuracy in all regions of the force strength χ by using the quasi-spin squeezed state. Also, it is shown that the quasi-spin squeezed state gives a classical counterpart with a certain correction for the Holstein-Primakoff boson representation of su(2)-spin. We investigate uncertainty relations for su(2)-generators and the meaning of “squeezing” is clarified.