Quantum mechanical analyses of nanoscale phonon transport

在JSPS基金资助下的研究成果主要包括三个方面：（1）发展了三维非谐声子非平衡绿色函数体系，并建立了大规模量子热输运模拟的并行计算框架。利用新的方法，利用局域谱能量交换分解方法，研究了非谐声子-声子散射在固-固界面热输运中的作用。 此外，我们还提出了一种新的途径来证明梯度超晶格中的声子局域化和量子相干区中的热导率极小现象。(2)我们开发了一个介观模拟框架的基础上声子玻尔兹曼方程Callaway的双弛豫模型与完全从头算输入的声子性质的各向同性和各向异性材料系统。利用该方法，我们研究了石墨纳米结构和微结构中声子流体力学的尺寸效应，并推动了微米级同位素纯化石墨带中声子Poillille流的实验观测。(3)我们发展了一个耦合模型，通过声子和表面声子极化激元沿沿着极性介电纳米结构的热传输。对表面声子极化激元导出了双极性薄膜中二维热输运的普适量子。由于耦合动力学的非线性温度分布也被证明。

The research achievements under the support of JSPS fellowship mainly include three aspects:(1) We develop the three-dimensional anharmonic phonon non-equilibrium Green’s function formalism, and a parallelized computational framework for large-scale quantum heat transport simulation. With the new methodology, the open question of how anharmonic phonon-phonon scattering plays the role in heat transport at solid-solid interface is studied with a local spectral energy exchange decomposition scheme. Also we present a novel path to demonstrate phonon localization in graded superlattices and a thermal conductivity minimum phenomenon in the quantum coherent regime.(2) We develop a mesoscopic simulation framework based on the phonon Boltzmann equation under Callaway’s dual relaxation model with fully ab initio input of phonon properties for both isotropic and anisotropic material systems. With the new method, we investigate the size effect of phonon hydrodynamics in graphitic nano- and micro-structures, and promote the experimental observation of phonon Poiseuille flow in micro-meter-scale isotopically purified graphite ribbon.(3) We develop a coupled model for heat transport along polar dielectric nanostructures via phonons and surface phonon polaritons. A universal quantum of two-dimensional heat transport in ultrathin polar films is derived for surface phonon polaritons. The non-linear temperature profile due to the coupled dynamics is also demonstrated.