Electrical transport and superconducting properties of thin tin-copper films

For tin-10 at% copper and tin films in a wide range of normal state sheet resistances, R_□N, the electrical resistance R_□(T) and the excess conductance σ′(T,H) due to superconducting fluctuations have been measured. The data on σ′(T,0) near T_c have been analyzed by the sum of Aslamazov-Larkin and Maki-Thompson terms. It has been found that there is a large difference of δ (pair breaking parameter in the MT term) between the tin-copper and tin films. The difference of R_□N-dependence of δ between the two systems can be explained in terms of the contribution δ_e-p = πℏ/8k_BTτ_e-p due to the electron-phonon inelastic scattering, by employing Thouless theory for the rate 1/τ_e-p and also the R_□N-dependence of the electrical transport properties for each system. An agreement between the experiment and theory suggests that the rate 1/τ_e-p for disordered thin-films is determined by not only electron mean free path ℓ but also resistivity ratio Γ (= ρ_{300 K} /ρ_{4.2 K}).