论文标题
二维材料中第二声音的统一理论
A unified theory of second sound in two dimensional materials
论文作者
论文摘要
我们在二维材料中为第二个声音开发了统一的理论。先前研究的漂移和无漂移的第二声音是该理论的两个限制案例，分别对应于能量通量的漂移和扩散部分。我们发现，由于存在二次弯曲声子，在热力学极限中不存在漂移的第二声音，而无漂移模式的影响较小。由于其恒定密度态和长波长度极限中的恒定密度态和发散的玻色 - 因斯坦分布，因此理解了这是由于无限有效的柔性惯性。因此，漂移模式的组速度小于无漂移模式的速度。但是，在拉伸应变时，漂流模式的速度变得更大。由于弯曲声子分散剂的线性化，它们都随着拉伸应变而增加。我们的结果阐明了以前遇到的几个难题，并为探索流体动力学方面的波动热传输铺平了道路。
We develop a unified theory for the second sound in two dimensional materials. Previously studied drifting and driftless second sound are two limiting cases of the theory, corresponding to the drift and diffusive part of the energy flux, respectively. We find that due to the presence of quadratic flexural phonons the drifting second sound does not exist in the thermodynamic limit, while the driftless mode is less affected. This is understood as a result of infinite effective inertia of flexual phonons, due to their constant density states and divergent Bose-Einstein distribution in the long wave length limit. Consequently, the group velocity of the drifting mode is smaller than that of the driftless mode. However, upon tensile strain, the velocity of drifting mode becomes larger. Both of them increase with tensile strain due to the linearization of the flexural phonon dispersion. Our results clarify several puzzles encountered previously and pave the way for exploring wave-like heat transport beyond hydrodynamic regime.
