We model the highly reduced thermal conductivity of nanostructured materials observed in nanoribbons. For highly scaled structures, such as wires with diameters on the order of 20 nm, physical effects beyond classical boundary scattering, including acoustic softening, become important. To date, work on acoustic softening has focused on reductions in group velocity. However, a reduction in the group velocity implies that the phonon dispersion is modified. Here, we investigate how changes in the phonon dispersion manifest in the mean free path, heat capacity, and group velocity. Including these effects in the modeling of thermal conductivity, we find that softening increases low-temperature thermal conductivity while reducing high temperature thermal conductivity. We further compare the model to experimental data.

中文翻译：

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声学软化对超过群速度的热导率的影响

我们模拟了在纳米带中观察到的纳米结构材料的高度降低的热导率。对于高度缩放的结构，例如直径约为 20 nm 的线，超出经典边界散射的物理效应（包括声学软化）变得很重要。迄今为止，声学软化的工作主要集中在降低群速度上。然而，群速度的降低意味着声子色散被修改。在这里，我们研究声子色散的变化如何在平均自由程、热容和群速度中表现出来。将这些影响包括在热导率建模中，我们发现软化会增加低温热导率，同时降低高温热导率。我们进一步将模型与实验数据进行比较。