Phonon transport and vibrational excitations in amorphous solids
Phonon transport and vibrational excitations in amorphous solids
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DOI：
10.1103/physreve.98.062612
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发表时间：
2018-04
影响因子：
2.4
通讯作者：
H. Mizuno;A. Ikeda
中科院分区：
文献类型：
--
作者：
H. Mizuno;A. Ikeda
关于非晶固体热性质的一个长期存在的问题是声子输运的复杂模式。实验和计算机模拟的最新进展表明，从瑞利散射到粘性阻尼的交叉。已经提出了一些理论，但缺乏关键的测试，这些理论的有效性尚不清楚。特别是，交叉频率的精确位置仍然存在争议，更关键的是，甚至瑞利散射本身的有效性也受到了严重质疑。目前的工作解决了这些问题，通过使用基本的振动本征模式的信息。振动本征模最近澄清了一个宽的频率制度：声子模式和软本地化模式的混合物中的连续极限和无序和扩展模式的玻色子峰制度。在这里，我们表明，瑞利散射发生在连续极限和粘性阻尼发生在玻色子峰值制度，这些行为，因此，在相应的频率制度的基础本征模。我们的结果明确地确定了交叉频率。此外，我们建立的特征标度律的声子输运，这是一致的平均场理论的预测在较高的频率，但不一致的低频，瑞利散射制度。因此，我们的研究结果揭示了当前理论有待解决的关键问题。
One of the long-standing issues concerning the thermal properties of amorphous solids is the complex pattern of phonon transport. Recent advances in experiments and computer simulations have indicated a crossover from Rayleigh scattering to viscous damping. A number of theories have been proposed, yet critical tests are missing and the validity of these theories is unclear. In particular, the precise location of the crossover frequency remains controversial, and more critically, even the validity of the Rayleigh scattering itself has been seriously questioned. The present work settles these issues by using information on the underlying vibrational eigenmodes. Vibrational eigenmodes were recently clarified over a wide frequency regime: a mixture of phonon modes and soft localized modes in the continuum limit and disordered and extended modes in the boson peak regime. Here, we demonstrate that Rayleigh scattering occurs in the continuum limit and viscous damping occurs in the boson peak regime, and these behaviors are therefore linked to the underlying eigenmodes in the corresponding frequency regimes. Our results unambiguously determine the crossover frequency. Furthermore, we establish characteristic scaling laws of phonon transport, which are consistent with the prediction of the mean-field theory at higher frequencies but inconsistent in the low-frequency, Rayleigh scattering regime. Our results therefore reveal crucial issues to be solved with regard to the current theory.