有限温度下二维Heisenberg铁磁系统的声子衰减

在二维正方Heisenberg铁磁系统的基础上建立了磁振子-声子相互作用模型. 利用松原格林函数理论研究了系统的声子衰减，计算了布里渊区的主要对称点线上的声子衰减曲线. 发现在第一布里渊区，在Δ线上，横向声频支声子无衰减，在Z线上，纵向声频支声子无衰减；横向声频支声子衰减比纵向声频支声子衰减至少大一个数量级，并讨论了各项参数的变化对横向声频支声子衰减与纵向声频支声子衰减的影响. 根据声子衰减与声子寿命的关系，声子衰减与声子态密度的关系，可以讨论横向声频支声子与纵向声频支声子的寿命与态密度. 关键词：磁振子-声子相互作用横向声频支声子衰减纵向声频支声子衰减声子寿命

Phonon damping in two-dimensional Heisenberg ferromagnetic system at finite temperature

A magnon-phonon interaction model is developed on the basis of two-dimensional square Heisenberg ferromagnetic system. The transverse acoustic phonon damping and longitudinal acoustic phonon damping are studied through Matsubara Green function theory, and transverse acoustic phonon damping and longitudinal acoustic phonon damping curves are calculated on the main symmetric point and line in the first Brillouin zone. It’s found that in the first Brillouin zone, on line Δ, there is no damping for the transverse acoustic phonon, on line Z, there is no damping for longitudinal acoustic phonon. In the first Brillouin zone, the transverse acoustic phonon damping is one order larger than the longitudinal acoustic phonon damping. The influences of transverse acoustic phonon damping and longitudinal acoustic phonon damping for different parameters on them are also illustrated in this article. According to the relationship between phonon damping and phonon lifetime, and the relationship between phonon damping and phonon density of state, the lifetime and density of state for transverse acoustic phonon and longitudinal acoustic phonon is discussed.