Phonon ray tracing calculations of ballistic temperature and heat flux profiles in nanostructures
Phonon ray tracing calculations of ballistic temperature and heat flux profiles in nanostructures
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DOI：
10.1016/j.mtphys.2023.101040
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发表时间：
2023-03
影响因子：
11.5
通讯作者：
Yingru Song;Geoff Wehmeyer
中科院分区：
文献类型：
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作者：
Yingru Song;Geoff Wehmeyer
声子射线追踪计算已被用于量化纳米材料中的声子边界散射和解释热导率测量。然而，基于兰道尔的声子射线追踪方法无法获得纳米材料内部的温度或热通量分布，这意味着需要计算密集型的玻尔兹曼输运方程求解器来深入了解弹道输运物理或模型纳米尺度温度映射实验。在这里，我们推导并应用声子蒙特卡罗射线追踪方法来计算半导体纳米材料中的局部温度和局部热通量，重点是弹道输运机制。推导提供了一个直接的解释，局部温度的热导比，和局部热通量的差异，正向和反向声子轨迹越过控制面。在验证了几种常见输运机制和几何形状的方法后，我们应用该方法来优化导致多孔纳米网格局部温度梯度倒置的几何参数，并评估几何弹道声子透镜的热聚焦能力。这些应用说明了声子射线追踪方法如何用于量化弹道热剖面和设计在弹道状态下表现出非典型热行为的纳米结构。
Phonon ray tracing calculations have been used to quantify phonon boundary scattering in nanomaterials and to interpret thermal conductivity measurements. However, Landauer-based phonon ray tracing methods have not been able to access the temperature or heat flux profiles within nanomaterials, meaning that computationally intensive Boltzmann Transport Equation solvers are needed to gain insight into ballistic transport physics or model nanoscale temperature mapping experiments. Here, we derive and apply phonon Monte Carlo ray tracing methods to calculate the local temperature and local heat flux in semiconducting nanomaterials, with a focus on the ballistic transport regime. The derivation provides a straightforward interpretation of the local temperature in terms of a thermal conductance ratio, and the local heat flux in terms of the difference between forward- and reverse-oriented phonon trajectories crossing a control surface. After validating the method for several common transport regimes and geometries, we apply the method to optimize geometric parameters that lead to locally inverted temperature gradients in porous nanomeshes, and to evaluate the heat focusing capabilities of geometric ballistic phonon lenses. These applications illustrate how phonon ray tracing methods can be used to quantify ballistic thermal profiles and to design nanostructures that exhibit atypical thermal behaviors in the ballistic regime.