低温下多通道量子结构中的弹性声子输运和热导

摘要

By using the elastic approximation model and scattering matrix method, we investigated the acoustic phonons transport and thermal conductance in a H-branch four-channel nanostructure. The calculated results show that, for the incident acoustic phonons of low frequency, as long as the transverse width of each channel is equal, the transmission coefficient of mode 0 in each channel almost equals 0. 25 and receives no influence from the changes of the other structure parameters.But for the incident acoustic phonons of high frequency, the transmission coefficient of mode 0 in each channel is very sensitive to the structure parameters and there is bigger difference corresponding to the transmission coefficients of different channels. When the temperature is very low, the thermal conductance in each channel is about 1/(4)π2k2BT/(3h). With the increase of temperature, the thermal conductance of each channel changes to different degrees. By changing the length of scattering region or the transverse width of each channel, we can control the separating degree of modes and the thermal conductance of each channel efficiently and realize acoustic phonon selective transport and thermal conduction.%利用弹性近似模型和散射矩阵方法,研究了低温下多通道量子结构中的弹性声学声子输运的性质.计算结果表明,对于低频声学声子,只要通道的横向宽度相同,各通道中最低阶模的透射概率几乎不受其他结构参数的影响,且其数值都接近于0.25;而高频声学声子在各通道中的透射概率与结构参数密切相关,不同通道中的透射概率不同;当温度非常低时,各通道的热导都接近于量子化热导π2k2BT/(3h)的四分之一;随着温度的升高,各通道的热导增减不一,不同通道的热导差异较大;改变结构参数能有效地调节各通道中声子模的分离程度和热导的大小,从而实现选择性声子输运和热传导.