Thermopower and the electron-phonon interaction in high-$T_c$ superconductors

The temperature dependence of metallic diffusion thermopower arising from electron-phonon enhancement is calculated for high-$T_c$ superconductors, in particular La-Sr-Cu-O. The potential usefulness of thermopower is demonstrated by a similar calculation for high-resistivity Chevrel superconductors, which gives an excellent description of their total thermopower and provides evidence for a normal electron phonon interaction. An analysis of diffusion thermopower in present measurements on metallic high-$T_c$ superconductors is prevented by phonon drag or other effects; measurements on more disordered samples are needed to permit a comparison with our calculations and help determine the role of the electron-phonon interaction in these systems.