零温时二维绝缘铁磁体的磁振子寿命

Magnon Lifetime of Two-Dimensional Insulating Ferromagnet at T=0?K

在二维正方绝缘铁磁系统基础上建立了一个磁振子-声子相互作用模型.利用格林函数方法研究了磁振子-声子相互作用下的二维绝缘铁磁体的磁振子衰减,计算了布里渊区的主要对称点线上的-ImΣ*(1)(k).发现在布里渊区边界区域磁振子衰减很明显,但小波矢区(kxa/π<0.22附近)磁振子衰减非常弱.零温时磁振子衰减有极大值.比较了纵向声子与横向声子对磁振子衰减的影响,也讨论了各项参数的变化对磁振子衰减的影响.根据关系式-ImΣ*(1)(k)=/(2τ)可以对磁振子寿命进行判断.

A magnon-phonon interaction model is developed for a two dimensional square insulating ferromagnet. By Matsubara-Green function method, the magnon damping under such on interaction is studied, with the magnon damping calculated on the main symmetric point/line in Brillouin zone for different parameters in the system. It is found that at the boundary of Brillouin zone the magnon damping is strong, while it is very weak in the zone of small wave vectors, and especially the magnon damping becomes maximal at T = 0 K. The influences of longitudinal pbonon and transverse phonon on the magnon damping are compared, and the influences of all relevant parameters on magnon damping are also discussed. The expression - Im∑＊（1）（k） = h（2τ） is available to take as a criterion for the magnon lifetime.