Study of Thermal Squeezed Effect of Magnons in the Ferromagnet

Study of Thermal Squeezed Effect of Magnons in the Ferromagnet
　　It is well known that squeezed state is one of non-classical states in the field of quantum optics. The idea of squeezed states can be used to reduce quantum noise in measuring high precise signal. So the research of the squeezed state of Bose has been an important research subject of physics research field.In this paper, we investigate the temperature dependent characteristic of magnon squeezed state and the phase distributed characteristic of Q distribution function magnet lifter in the squeezed state. Therefore, firstly we introduce Holstein-Primakoff transformation to deal with the nonlinear magnon-magnon interaction in the spin system. Then we introduce the Bogoliubov transformation to eliminate the fourth order nondiagonal terms and introduce temperature dependent number functor.
　　Under the mean-field field approximation, we acquire the pair Hamiltonian of the magnon system. Subsequently, we study the temperature dependent magnon quantum fluctuation at the low temperature. We find that spin fluctuation in the one of spin components can be lower than that of vacuum fluctuation in some given periodical time. The squeezed effect reduce going with magnet lifter temperature rising. When the temperature achieve to its limit, the squeezed effect disappears. At the same time, we investigate the temperature dependent phasic characteristic of Q distribution function in the squeezed thermal spin state. We find that the variation ofQ distribution function depends strongly on the temperatureT and coupling parameterγ. In the squeezed thermal magnet lifter spin state, the phase symmetry of the magnon system is spontaneously broken.