Kapitza thermal resistance between a metal and a nonmetal

The thermal boundary conductance is derived for the heat flow between the electrons in a metal and the phonons in an ionic crystal. The image potential generated by the ion charges makes a regular pattern of surface charges on the surface of the metal. When the ions vibrate, these surface charges oscillate. Since the surface charges are the tails of the wave functions of the conduction electrons in the metal, the surface charges provide a matrix element between these electrons and the phonons in the insulator.