报告专家：熊世云

报告时间：2020年7月9日 周四下午14:00

报告地点：行健楼436

报告摘要：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[1]. To create phonon resonances, either periodic resonant structures[1-2] or surface amorphous structures[3] can be used. The former one can create regular resonances while the later one can create dispersionless (random) resonant modes. Differing from the phonon scattering mechanism, which is under the assumption of phonon particle picture and blocks the high frequency phonon transport efficiently, the resonant mechanism adopts the phonon wave effect. The resonant mechanism is extremely powerful to hinder the low frequency phonon transport, i.e., it is able to block phonon transport in wavelengths much longer than the size and period of the surface resonant structures[3-7]. As a result, the phonon resonant mechanism can complement with the phonon scattering mechanism to efficiently stop the phonon transport in the whole frequency range. The hinderance of low frequency phonon transport by phonon resonances relies on the large reduction of both group velocity and relaxation time. We also demonstrate the detailed mechanisms for creating the resonances and the tunability of resonant frequency, strength by resonant structure size, mean free path in resonant structures, interface qualities. A further consequence of using resonant structures is that they are not expected to scatter electrons, which is beneficial for thermoelectric applications.

参考文献：

1. Shiyun Xiong*, Kimmo Saaskilahti, Yuriy A. Kosevich, Haoxue Han, Davide Donadio, Sebastian Volz, Blocking phonon transport by structural resonances in alloy-based nanophononic metamaterials leads to ultralow thermal conductivity, Phys. Rev. Lett. 117 (2016) 025503

2. B. L. Davis, M. I. Hussein, Nanophononic metamaterial: Thermal conductivity reduction by local resonance, Phys. Rev. Lett.112 (2014) 055505

3. Shiyun Xiong*, Daniele Selli, Sanghamitra Neogi, Davide Donadio*, Native surface oxide turns alloyed silicon membranes into nanophononic metamaterials with ultralow thermal conductivity, Phys. Rev. B 95 (2017) 180301(R)

4. Shiyun Xiong, Sebastian Volz, Nanostructuration for thermoelectricity: The path to an unlimited reduction of phonon transport, Comptes Rendus Physique 17 (2016) 1146

5. Yinchun Wan#, Shiyun Xiong#, Bin Ouyang, Zhihui Niu, Yuxiang Ni, Yu Zhao, Xiaohong Zhang, Thermal Transport Engineering in Graphdiyne and Graphdiyne Nanoribbons, ACS Omega, 4 (2019) 4147

6. Hongying Wang, Yajuan Cheng, Masahiro Nomura, Sebastian Volz, Davide Donadio, Shiyun Xiong*, Synergistic engineering of phonon transport through resonances and screw dislocations (submitted)

7. Hongying Wang, Yajuan Cheng, Shiyun Xiong*, Xiaohong Zhang*, Quantifying phonon resonant mechanism in branched graphene nanoribbons (to be submit)

报告人简介：熊世云，苏州大学功能纳米软物质研究院副教授，2014年于法国巴黎中央理工学院取得博士学位。  近年来在Phys. Rev. Lett, Small, Phys. Rev. B等权威期刊上发表SCI论文30余篇，在国际会议上报告研究成果10余次，其中做邀请报告1次；部分研究工作被其他研究者跟踪研究或被国外专著引用，所建立的模型被多次被用来解释实验现象；受邀以第一作者为Scholar's Press撰写专著一部；具体主要成果包括：首次研究了热传导到近场辐射的转变及相关机制；系统的研究了缺陷对纳米尺度热传导的影响；建立了多个表征纳米材料热力学性能（如相变、溶化熵、合金化）随尺寸及形状变化的模型。