多通道石墨纳米带中弹性声学声子输运和热导特性

采用非平衡格林函数方法, 在保持总的能量输出通道中石墨链数不变的条件下, 研究并比较了并列的石墨纳米带通道中弹性声学声子输运和热导特性. 结果表明, 能量输出通道的增加能降低每个能量输出通道的热导; 与能量输入热库最近的能量输出通道热导最大, 最远的能量输出通道热导最小; 中间能量输出通道的热导性质与并列的各输出通道的结构参数密切相关, 最近和最远的能量输出通道的热导性质仅与各自能量输出通道的结构参数有关; 粗糙边缘结构能有效调节各通道的热导; 总的热导性质与能量输出通道石墨链数、能量输出通道数以及边缘结构粗糙程度密切相关.

Characteristics of acoustic phonon transport and thermal conductance in multi-terminal graphene junctions

By using non-equilibrium Green’s function method, we investigate the transmission rate of acoustic phonon and thermal conductance through a parallel multi-terminal graphene junctions, the relationship between the thermal-transport property in each terminal and the number of quantum terminals, the relationship between the thermal-transport property in each terminal and the relative position of quantum terminals in quantum structure, and also study the thermaltransport property in each terminal and the rough degree of edge structure. The results show that when the graphene chains (dimer lines) across the ribbon width are fixed, the increase of the number of the parallel multi-terminal graphene junctions can reduce the transmission rate of the phonons and the thermal conductance of each output terminal as well. This is because the increase of the number of the graphene junctions can lead to the decrease of the transverse dimension of the each output terminal, which enlarges the strength of the phonon scattering and results in the reduction of the phonon transmission. Owing to long distance scattering, the transmission rate of the phonons of the furthest distant output terminal is the smallest, and also the thermal conductance of the furthest output terminal is the smallest. On the contrary, the strength of the phonon scattering is the weakest for the closest output terminal. So the transmission rate of the phonons is the biggest, which induces the thermal conductance to be the biggest. The thermal conductance of the middle-output terminal depends sensitively on the structural parameters of each terminal. This is because mainly the relative position between the middle-output terminal and the phonon-input terminal is related closely to the structural parameters of each terminal, which can influence the strength of the phonon scattering and the transmission rate of the phonons. However, the thermal conductances in the top and bottom output terminals are just sensitively dependent on the structural parameters of the respective output terminal. This is because the relative position between the top (or bottom) output terminal and the phonon-input terminal is only related to the structural parameters of the respective output terminal. The rough edge structure can reduce obviously the transmission rate of the phonons, and the thermal conductance of the closest output terminal as well. The rough edge structure can modulate slightly the transmission rate of the phonons and the thermal conductance of the other output terminal. The total thermal conductance is related closely to the number of total graphene chains, the number of the multi-terminal graphene junctions, and the rough degree of edge structure. These results shed new light on the understanding of the thermal transport behaviors of multi-terminal junction quantum devices based on graphene-based nanomaterials in practical application.