论文标题
波与粒子声子在通过纳米结构的热传输中的影响
Effect of wave versus particle phonon nature in thermal transport through nanostructures
论文作者
论文摘要
对纳米结构材料中热传输的全面理解需要大尺度模拟桥接长度尺度，由与声子的波和粒子性质相关的不同物理学决定。然而，可用的计算方法隐式将声子视为波浪或粒子。在这项工作中，使用基于全波的非平衡绿色功能（NEGF）方法以及基于粒子的射线追踪蒙特卡洛（MC）方法，我们研究了纳米级特征附近的波和基于粒子基于粒子的声子传输的定性差异。对于纳米多孔几何形状的简单示例，我们表明，对于这两种方法，声子传输都很好地吻合，误差余量约为15％，即使尺寸降低到3-4 nm，跨音子波长也是如此。对于需要在较小区域挤压的情况下，我们发现MC低估了长波长声子的传输，而NEGF内的波浪处理表明那些长波长的声子可以更容易地传播。我们还发现，与基于波浪的NEGF方法相比，基于粒子的仿真方法对结构变化更为敏感。从比较波和粒子方法中提取的见解可用于提供对纳米材料中声子传输的更好，更完整的理解。
Comprehensive understanding of thermal transport in nanostructured materials needs large scale simulations bridging length scales dictated by different physics related to the wave versus particle nature of phonons. Yet, available computational approaches implicitly treat phonons as either just waves or as particles. In this work, using a full wave-based Non-Equilibrium Green's Function (NEGF) method, and a particle-based ray-tracing Monte Carlo (MC) approach, we investigate the qualitative differences in the wave and particle-based phonon transport at the vicinity of nanoscale features. For the simple example of a nanoporous geometry, we show that phonon transmission agrees very well for both methods with an error margin of approximately 15%, across phonon wavelengths even for features with sizes down to 3-4 nm. For cases where phonons need to squeeze in smaller regions to propagate, we find that MC underestimates the transmission of long wavelength phonons whereas wave treatment within NEGF indicates that those long wavelength phonons can propagate more easily. We also find that particle-based simulation methods are somewhat more sensitive to structural variations compared to the wave-based NEGF method. The insight extracted from comparing wave and particle methods can be used to provide a better and more complete understanding of phonon transport in nanomaterials.
