Crossover of ballistic, hydrodynamic, and diffusive phonon transport in suspended graphene
Crossover of ballistic, hydrodynamic, and diffusive phonon transport in suspended graphene
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DOI：
10.1103/physrevb.99.085202
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发表时间：
2018-11
影响因子：
3.7
通讯作者：
Xun Li;Sangyeop Lee
中科院分区：
文献类型：
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作者：
Xun Li;Sangyeop Lee
流体动力学声子输运最近被预测为石墨材料中声子输运的一种重要机制。过去许多关于流体动力学声子输运的研究都集中在流体动力学机制在其他机制中占主导地位的情况，这样流体动力学特征就能被清晰地观察到。然而，这通常需要严格的温度和样品尺寸条件。在很多情况下，单一机制并不会在其他机制中占主导，而是弹道、流体动力学和扩散这三种机制在一定程度上都存在。在这里，我们通过比较三种不同机制的动量破坏率来评估这三种机制的程度，每种机制代表一种不同的机制：无内部声子散射的漫反射边界散射（弹道机制）、与正常散射相结合的漫反射边界散射（流体动力学机制）以及反转散射（扩散机制）。我们使用偏差蒙特卡罗方法，用从头算全散射矩阵求解了皮尔斯 - 玻尔兹曼方程。我们分别对弹道粒子和散射粒子的分布函数进行采样，从而比较三种不同机制的动量破坏率。利用这个框架，我们讨论了一个著名的从弹道到流体动力学的转变现象，称为声子克努森极小值。
Hydrodynamic phonon transport was recently predicted as an important regime for phonon transport in graphitic materials. Many of past studies on hydrodynamic phonon transport have focused on the cases where the hydrodynamic regime predominates over other regimes such that hydrodynamic features can be clearly observed. However, this often requires stringent conditions of temperature and sample size. In many cases, a single regime does not dominate other regimes, but all three regimes - ballistic, hydrodynamic, and diffusive regimes - exist to some extent. Here we assess the extent of three regimes by comparing momentum destruction rates by three different mechanisms, each of which represents a different regime: diffuse boundary scattering without internal phonon scattering (ballistic regime), diffuse boundary scattering combined with normal scattering (hydrodynamic regime), and umklapp scattering (diffusive regime). We solve the Peierls-Boltzmann equation with an ab initio full scattering matrix using a deviational Monte Carlo method. We sample distribution functions of ballistic and scattered particles separately, and thereby compare the momentum destruction rates by the three different mechanisms. Using this framework, we discuss a well-known phenomenon of ballistic-to-hydrodynamic crossover, called phonon Knudsen minimum.