Onset of nondiffusive phonon transport in transient thermal grating decay
Onset of nondiffusive phonon transport in transient thermal grating decay
复制标题
DOI：
10.1103/physrevb.84.195206
复制
发表时间：
2011-11-28
影响因子：
3.7
通讯作者：
Nelson, Keith A.
中科院分区：
文献类型：
--
作者：
Maznev, A. A.;Johnson, Jeremy A.;Nelson, Keith A.
本文从理论上研究了介质晶体在德拜温度附近或更高温度下的空间正弦温度扰动的弛豫。我们假设，大多数声子贡献的比热有一个平均自由程（MFP）比热输运距离短得多，可以描述的热扩散模型。低频声子，可能有MFP相当于或长于光栅周期的玻尔兹曼传输方程描述。这些低频声子被假定为与高频声子的热库相互作用，但彼此不相互作用。在单模弛豫时间近似下，得到了热光栅弛豫速率的解析表达式。我们发现，“弹道”声子与长MFP的有效热导率控制的光栅衰减的贡献被抑制相比，他们的贡献，在长距离的热传输。在室温下的有效热导率在Si中的减少被发现是显着的光栅周期大至10 μ m。
The relaxation of a spatially sinusoidal temperature perturbation in a dielectric crystal at a temperature comparable to or higher than the Debye temperature is investigated theoretically. We assume that most phonons contributing to the specific heat have a mean free path (MFP) much shorter than the thermal transport distance and can be described by the thermal diffusion model. Low-frequency phonons that may have MFP comparable to or longer than the grating period are described by the Boltzmann transport equation. These low-frequency phonons are assumed to interact with the thermal reservoir of high-frequency phonons but not with each other. Within the single mode relaxation time approximation, an analytical expression for the thermal grating relaxation rate is obtained. We show that the contribution of "ballistic" phonons with long MFP to the effective thermal conductivity governing the grating decay is suppressed compared to their contribution to thermal transport at long distances. The reduction in the effective thermal conductivity in Si at room temperature is found to be significant at grating periods as large as 10 mu m.