arXiv 2103.016112021-03-02cond-mat.mes-hall

从热谱实验中重建声子谱性质的两种方法比较

Comparison on two ways of phonon spectral property reconstruction from thermal spectroscopy experiment

Mojtaba Forghani, Nicolas G. Hadjiconstantinou

摘要：

我们研究的可靠性的累积热导率作为一个功能的自由程，$F(Λ)$，在重建的背景下，声子输运性质的热光谱实验。我们特别表明，一个给定的$F(Λ)$不对应于一个独特的弛豫时间函数，在这个意义上说，一个以上的弛豫时间分布可以导致相同的$F(Λ)$。由于不同的弛豫时间分布通常会导致不同的热响应，因此$F(Λ)$不能唯一地预测所有输运状态下的材料热响应。这意味着，在玻尔兹曼弛豫时间近似框架内的纳米尺度下的热输运的背景下，应该从热光谱实验中重建的基本属性是频率依赖的弛豫时间函数（假设群速度是已知的），因为它明确地出现在控制方程中作为输入材料属性。广泛的全局优化研究表明，先前提出的基于频率相关弛豫时间函数的重建公式[Physical Review B 94，155439（2016）]提供了数值上唯一的解决方案。

英文摘要：

We examine the reliability of the cumulative thermal conductivity as a function of the free path, $F(Λ)$, in the context of reconstruction of phonon transport properties from thermal spectroscopy experiments. We specifically show that a given $F(Λ)$ does not correspond to a unique relaxation-times function, in the sense that more than one distribution of relaxation-times can result in the same $F(Λ)$. Since different relaxation-time distributions will, in general, lead to different thermal responses, $F(Λ)$ does not uniquely predict the material thermal response in all transport regimes. This implies that in the context of thermal transport at the nanoscale within the Boltzmann relaxation-time approximation framework, the fundamental property that should be reconstructed from the thermal spectroscopy experiments is the frequency-dependent relaxation-times function (provided group velocities are known), since it explicitly appears in the governing equation as the input material property. Extensive global optimization studies show that a previously proposed formulation for reconstruction based on the frequency-dependent relaxation-times function [Physical Review B 94, 155439 (2016)] provides numerically unique solutions.

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