Phonon-induced electron-electron interaction in disordered superconductors

We have measured the resistivities as a function of temperature of crystalline disordered bulk Ti1-xAlx-y(Co,Cr,Au)y (x 0.072) alloys below 25 K. With a total doping level of 7.2 at. % for Ti, our samples are disordered enough to manifest electron-electron interaction effects. As the temperature T is reduced, a resistivity increase Δρ(T)/ρ(10 K) = [ρ(T)-ρ(10 K)]/ρ(10 K) on the order of a tenth of a percent is observed in all alloys before they eventually undergo superconducting transitions at sufficiently low T (depending on y). Both the functional forms and magnitudes of the observed Δρ(T)/ρ(10 K) are interpreted in terms of electron-electron interaction effects in the presence of disorder. Particularly, the values of the screened Coulomb interaction parameter F defined in electron-electron interaction theory are extracted. In the Coa from that of Ti1-xAlx, we find that the electron-phonon coupling, including exchange of virtual phonons, is of crucial importance in determining the value of F. However, the theory for F in its current form fails to account for our experimental results. In the Au-doped alloys, the spin-orbit scattering introduced by the heavy Au atoms causes a small decrease in the value of F, i.e., F becomes slightly more negative for higher spin-orbit scattering.