基于声子局域共振机制调控分支型纳米带热输运性质的研究

研究热输运性质对纳米结构在电子信息和新能源器件方面的应用至关重要。通过控制声子的非谐散射(粒子性)或实现相干声子输运（波动性)可以调控纳米结构的热输运性质，但两者都存在明显的局限性，亟需探索新的物理机制和调控方案。本项目拟采用非平衡格林函数方法、分子动力学模拟，结合晶格动力学理论，系统地研究声子局域共振机制对分支型纳米带热传导的影响，重点探索：(1)几何尺寸、分支构型、环境温度等因素对体系热导率的影响，以确定声子共振强弱的最佳参数范围；(2)分析空位散射、杂质散射、应力场散射等散射机制与声子局域共振机制的内在关联，研究在声子散射—局域共振协同作用下分支型纳米带体系中的新奇热输运现象，并建立定量区分两类机制对热导率贡献的物理模型，实现对全频域声子输运调控的目的；(3)基于分支型纳米带的热电和热管理器件的理论设计。本项目的开展有助于完善声子输运理论，为调控纳米结构热输运性质提供科学依据。

The study of thermal transport properties in nanostructures is crucial for their applications in electronic devices for information and new energy-conversion devices. There are normally two approaches to manipulate the thermal transport properties of nanostructures: one is changing anharmonic phonon scattering (particle-like) and the other is realizing coherent phonon transport (wave-like). However, both of them have obvious limitations, therefore it is urgent to explore new physical mechanisms and regulation schemes. In this project, the influence of phonon local resonance on heat conduction in branched nanoribbons will be systematically studied by nonequilibrium Green's-function method and molecular dynamics simulations, as well as lattice kinetic theory. We will focus on: (1) investigating the effects of geometry size, branch configuration and ambient temperature etc. on thermal conductivity in branched nanoribbons to ascertain the best parameters of the resonance intensity; (2) understanding the intrinsic relevance between various phonon scattering mechanisms such as vacancy scattering, impurity scattering, stress scattering etc. and phonon local resonance mechanism, exploring the novel phenomenon of thermal transport in branched nanoribbons under the synergism of phonon scattering—local resonance, and establishing a physical model for quantitatively distinguishing the contribution from two kinds of mechanisms to thermal conductivity; (3) designing thermoelectric devices and thermal management devices on the base of branched nanoribbons. This project will be helpful for improving the theory of phonon transport, and will provide the scientific evidence for regulating thermal transport properties in nanostructures.