Morphic effects. III - Effects of an external magnetic field on the long wavelength optical phonons.
Morphic effects. III - Effects of an external magnetic field on the long wavelength optical phonons.
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变形效果。
DOI：
10.1016/0022-3697(72)90034-0
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发表时间：
1972
期刊：
影响因子：
--
通讯作者：
R. Minnick
中科院分区：
文献类型：
--
作者：
E. Anastassakis;E. Burstein;A. Maradudin;R. Minnick
对非磁性晶体施加静态外部磁场时，k≈0 光学振动模式的频率变化被确定为场强的一阶。二阶效应相当于二阶电场的效应，这里不予考虑。结果表明，非简并模式的频率在磁场中不会改变为一阶。在非立方晶体结构的情况下，我们发现磁场必须具有沿最高对称轴的分量，以便双简并模式 atk ≈ 0 的简并度得以提升。在立方结构的情况下，在任何方向施加的磁场都可以完全分裂三重简并atk≈0的模式的简并性。给出了简正模式频率中场引起的变化的表达式。发现频率偏移的模式是右圆偏振或左圆偏振。简要讨论了空间色散效应，即声子波矢量中线性模式简并的分裂。最后，对声学活动的对称性和声学声子的法拉第效应进行了回顾。
The changes in the frequencies of thek≈ 0 optical vibration modes on the application of a static, external magnetic field to a non-magnetic crystal are determinedto first order in the field strength. Second order effects are equivalent to the effects of an electric field in second order and they are not considered here. It is shown that the frequency of a nondegenerate mode is not altered to first order in the magnetic field. In the case of the noncubic crystal structures it is found that the magnetic field must have a component along the axis of highest symmetry in order that the doubly degenerate modes atk≈ 0 have their degeneracy lifted. In the case of the cubic structures a magnetic field applied in any direction can completely split the degeneracy of modes which are triply degenerate atk≈ 0. Expressions are given for the field induced changes in the normal mode frequencies. The modes whose frequencies are shifted are found to be right or left circularly polarized. A brief discussion is given of spatial dispersion effects, that is, splitting of the mode degeneracy linear in the phonon wave-vector. Finally, a review of the symmetry aspects of acoustical activity and Faraday effects of acoustical phonons is presented.