The control of thermal waves by the phononic crystal exhibits peculiar behaviors different from the particle picture of phonons and thus has attracted increasing interest. However, the wave nature of phonons is only indirectly reflected in most studies via the macroscopic thermal transport coefficient, such as thermal conductivity. In this work, we investigate directly the coherent interference effect in a graphene superlattice structure at the microscopic phonon mode level via wave-packet simulations. The constructive interference and destructive interference between the reflected phonons give rise to valleys and peaks in the transmission coefficient, respectively, leading to the periodic oscillation of the transmission function with the variation of the superlattice period length. More importantly, both total-transmission and total-reflection of individual phonons have been clearly demonstrated. The physical conditions for realizing the phonon interference have been proposed, which are quantitatively in good agreement with independent wave-packet simulations. Our study provides direct evidence for the coherent phonon interference effect, which might be helpful for the regulation of phonon transport based on its wave nature.

中文翻译：

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声子晶体纳米结构中单个声子的全透射和全反射

由声子晶体控制热波表现出与声子的粒子图像不同的特殊行为，因此引起了越来越多的兴趣。但是，在大多数研究中，声子的波性仅通过宏观的热传导系数（例如导热系数）间接反映出来。在这项工作中，我们通过波包模拟直接研究了微观声子模式水平下石墨烯超晶格结构中的相干干涉效应。反射声子之间的相长干涉和相消干涉分别导致透射系数的谷值和峰值，从而导致透射函数的周期性振荡，而超晶格周期长度会发生变化。更重要的是，各个声子的全透射和全反射都得到了清晰的证明。提出了实现声子干扰的物理条件，这些条件在数量上与独立的波包模拟非常吻合。我们的研究为相干声子干涉效应提供了直接的证据，这可能有助于调节声子的波动性质。