Spin squeezing: thermal behavior and distribution on excited states

We investigate the spin-squeezing behavior under thermal effects in a one-dimensional transverse field XY model with spin-1/2. The exact solution of the model helps us to compute the spin-squeezing parameter as a function of temperature and also in all excited states with higher energy than the ground state. We find that below the thermal factorized field, hf(Tco), there is no transition temperature. At the thermal factorized field, a transition from a thermal squeezed state to an unsqueezed state occurs at a specific temperature called the “coherent temperature”. Interestingly, we show that the finite temperature can create squeezed states from a state which at zero temperature is a coherent state. To complete our study, we also analyze the variation of the spin-squeezing parameter in the excited states and provide a behavioral analysis of the thermal spin-squeezing parameter.