Max Planck Institute for Polymer Research, Ackermannweg 10, 55218 Mainz, Germany.
CNRS, UPR 288 Laboratoire d'Energétique Moléculaire et Macroscopique, Combustion (EM2C), Ecole Centrale Paris, Grande Voie des Vignes, 92295 Châtenay-Malabry, France.
Phys Rev Lett. 2016 Jul 8;117(2):025503. doi: 10.1103/PhysRevLett.117.025503.
Understanding the design rules to obtain materials that enable a tight control of phonon transport over a broad range of frequencies would aid major developments in thermoelectric energy harvesting, heat management in microelectronics, and information and communication technology. Using atomistic simulations we show that the metamaterials approach relying on localized resonances is very promising to engineer heat transport at the nanoscale. Combining designed resonant structures to alloying can lead to extremely low thermal conductivity in silicon nanowires. The hybridization between resonant phonons and propagating modes greatly reduces the group velocities and the phonon mean free paths in the low frequency acoustic range below 4 THz. Concurrently, alloy scattering hinders the propagation of high frequency thermal phonons. Our calculations establish a rationale between the size, shape, and period of the resonant structures, and the thermal conductivity of the nanowire, and demonstrate that this approach is even effective to block phonon transport in wavelengths much longer than the size and period of the surface resonant structures. A further consequence of using resonant structures is that they are not expected to scatter electrons, which is beneficial for thermoelectric applications.
理解获得材料的设计规则，使声子输运在很宽的频率范围内得到紧密控制，将有助于在热电能源收集、微电子热管理以及信息和通信技术方面取得重大进展。我们通过原子模拟表明，依赖局域共振的超材料方法在纳米尺度上进行热输运工程非常有前景。将设计的共振结构与合金相结合，可以导致硅纳米线的热导率极低。在低于 4THz 的低频声范围内，共振声子和传播模式之间的杂化大大降低了群速度和声子平均自由程。同时，合金散射阻碍了高频热声子的传播。我们的计算在共振结构的大小、形状和周期与纳米线的热导率之间建立了一个基本原理，并证明这种方法甚至可以有效地阻止比表面共振结构的大小和周期长得多的波长的声子输运。使用共振结构的另一个结果是，它们预计不会散射电子，这对于热电应用是有益的。
