Group velocities of phonons in superlattices
Group velocities of phonons in superlattices
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超晶格中声子的群速度
DOI：
10.1103/physrevb.65.174301
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发表时间：
2002
影响因子：
3.7
通讯作者：
S. Tamura
中科院分区：
文献类型：
--
作者：
K. Imamura;Yoshikazu Tanaka;S. Tamura
我们从理论上研究了周期超晶格中声子群速度的大小。利用色散关系计算了完美周期（无限）超晶格中的群速度，利用定相近似从声子波包的运动中定义了有限超晶格中的群速度。在一个频带内，无限和有限超晶格中的群速度是重合的。在频率间隙内，它们在有限超晶格中的幅度远大于在带区的幅度，并随着周期N的增加而增大。根据相应无限超晶格中的间隙是由于模内反射还是模间反射，这种N依赖性在性质上是不同的。为了解释声子群速度的这些不寻常行为，我们开发了基于传递矩阵方法的分析计算。给出了夹在GaAs衬底层和GaAs帽层之间的GaAs/AlAs超晶格的数值算例。
We theoretically study the magnitude of the group velocities of acoustic phonons in periodic superlattices. The group velocities in a perfect, periodic (infinite) superlattice are calculated from the dispersion relations and those in a finite superlattice are defined from the motion of phonon wave packets with the help of the stationary-phase approximation. In a frequency band, the group velocities in the infinite and finite superlattices coincide with each other. In a frequency gap, their magnitude in the finite superlattice becomes much larger than that in the band region, and increases as the periodicity N increases. This N dependence is qualitatively different depending on whether the gap in the corresponding infinite superlattice is due to the intramode or intermode Bragg reflection. To explain these unusual behaviors of phonon group velocities, we develop analytical calculations based on the transfer-matrix method. Numerical examples are given for a GaAs/AlAs superlattice sandwiched between GaAs substrate layer and GaAs cap layer.