ELECTRONIC KAPITZA CONDUCTANCE AT A DIAMOND-PB INTERFACE

In recent experiments it was found that the Kapitza conductance between diamond and Pb at room temperature is as much as 100 times larger than predicted by the acoustic mismatch model. Because the diamond and Pb are in intimate contact, the phonon modes near the interface are joint vibrational modes, extending a phonon mean free path on each side of the interface. Since the phonon mean-free path at room temperature is of the order of 4000 angstrom in diamond but only of the order of 10 angstrom in Pb, the energy of a joint mode resides primarily in the diamond. Consequently, the thermal population of a joint mode is determined by the temperature of the diamond. It is shown here that the direct energy transfer between metallic electrons at the Pb temperature and joint vibrational modes at the diamond temperature explains the observed heat conduction across the interface.