Ballistic Landauer-type thermal conductivity of a dielectric point contact

The contribution of the phonon diffraction effects to the thermal conductivity of dielectric and metal-dielectric point contacts is investigated. A formula analogous to the Landauer formula for electron conductivity holds for the thermal conductivity of the contact. Measurements of the heat flux of Si-Cu point contacts reveal a well-defined diffraction maxima of reduced thermal conductivity of the point contacts at temperatures 0.5-1 K.