Institute of Industrial Science, the University of Tokyo, Tokyo 153-8505, Japan.
Laboratory for Integrated Micro Mechatronic Systems/National Center for Scientific Research-Institute of Industrial Science (LIMMS/CNRS-IIS), the University of Tokyo, Tokyo 153-8505, Japan.
Nat Commun. 2017 May 18;8:15505. doi: 10.1038/ncomms15505.
Unlike classical heat diffusion at macroscale, nanoscale heat conduction can occur without energy dissipation because phonons can ballistically travel in straight lines for hundreds of nanometres. Nevertheless, despite recent experimental evidence of such ballistic phonon transport, control over its directionality, and thus its practical use, remains a challenge, as the directions of individual phonons are chaotic. Here, we show a method to control the directionality of ballistic phonon transport using silicon membranes with arrays of holes. First, we demonstrate that the arrays of holes form fluxes of phonons oriented in the same direction. Next, we use these nanostructures as directional sources of ballistic phonons and couple the emitted phonons into nanowires. Finally, we introduce thermal lens nanostructures, in which the emitted phonons converge at the focal point, thus focusing heat into a spot of a few hundred nanometres. These results motivate the concept of ray-like heat manipulations at the nanoscale.
与宏观尺度上的经典热扩散不同，纳米尺度的热传导可以在不耗散能量的情况下发生，因为声子可以在数百纳米的距离内直线弹道传播。然而，尽管最近有实验证据表明存在这种弹道声子输运，但对其方向性的控制，从而对其实际应用的控制仍然是一个挑战，因为单个声子的方向是混沌的。在这里，我们展示了一种使用具有孔阵列的硅膜来控制弹道声子输运方向性的方法。首先，我们证明了这些孔阵列形成了沿同一方向定向的声子流。接下来，我们将这些纳米结构用作弹道声子的定向源，并将发射的声子耦合到纳米线中。最后，我们引入了热透镜纳米结构，其中发射的声子在焦点处汇聚，从而将热量聚焦到几百纳米的一个点上。这些结果激发了在纳米尺度上进行类似光线的热操纵的概念。
