Electron-electron scattering in copper and silver from radio-frequency size effect measurements

Abstract

High-precision measurements of the scattering rates nu (T) in Cu and Ag have been performed between 0.5 and 8 K for electrons on extremal belly orbits perpendicular to the (111) and (110) directions. The behaviour of he electron-phonon contribution nu ep(T) can be accounted for with simple models which include a change in scattering effectiveness with temperature and energy averaging of the scattering rate. A term nu ee= alpha T2 from electron-electron scattering is observed and can even be dominating in Cu below 1.5 K when the electron-phonon collisions are made ineffective by decreasing the radio-frequency to 10 kHz. The value of alpha is nearly independent of the radio-frequency used. It amounts to 2.4*106 s-1 K-2 for the (111) orbit and 2.0*106 for the (100) orbit in Cu and 1.7*106 and 1.0*106 s-1 K-2 for the same orbits in Ag. These results are compared with data from transport measurements and with theoretical calculations.