Study Of Squeezing States Of Magnons In A Ferromagnet

Many non-classical states have been found in the field of quantum mechanics, among which is the squeezing state. In general, according to the requirements of the uncertainty principle, a squeezed state may have lower quantum fluctuation in one quadrature than that in a coherent state, while another quadrature is greater than that of a coherent state. The idea of the squeezing states can be used to reduce quantum noise in measuring high precise signal. So the research of the squeezing state of Bose has been the important research subject of physics research field.The spins of all electrons in each unit cell are parallel to each other in the ground state of ferromagnet and this is different from antiferromaget. Analogy to boson such as phonon and photon, the elementary excitation of spin wave is magnon. In ferromagnet system we considerate the high order of the Hamiltonian,the magnons of opposite wave vectors always appear simultaneously, there is an attractive magnon-magnon interaction which leads to bound magnon pairs. So the squeezing states originate from the nonlinear interaction of magnons. In this paper we mainly study the squeezing states of magnons in ferromagnet, the fluctuation of the spins components in the squeezing states can be lower than the fluctuation in the vacuum states. Through studying the dynamical and quantum fluctuation properties of the spin waves, in analogy with the modulation of quantum noise in light and lattice waves, and lattice waves, we calculate out the average value of spin fluctuation and get the condition of achieving the magnon squeezing states. In the course of calculating, we introduce the mean field theory to deal with the nonlinear interaction term of Hamiltonian of magnon system. At last we experimentally detected the squeezing magnons of the ferromagnet and discuss the value of the squeezing states.