Ballistic phonon transport and thermal conductance in multi-channel quantum structure at low temperatures

Abstract

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.