PHONON-INDUCED ELECTRON-ELECTRON INTERACTION IN DISORDERED SUPERCONDUCTORS

We have measured the resistivities as a function of temperature of cry stalline disordered bulk Ti(1-x)al(x-y)(Co,Cr,Au)(y) (x approximate to 0.072) alloys below 25 K. With a total doping level of 7.2 at % for T i, our samples are disordered enough to manifest electron-electron int eraction effects. As the temperature T is reduced, a resistivity incre ase Delta rho(T)/rho(10 K) = [rho(T)-rho(10 K)]/rho(10 K) on the order of a tenth of a percent is observed in all alloys before they eventua lly undergo superconducting transitions at sufficiently low T (dependi ng on y). Both the functional forms and magnitudes of the observed Del ta rho(T)/rho(10 K) are interpreted in terms of electron-electron inte raction effects in the presence of disorder. Particularly, the values of the screened Coulomb interaction parameter ($) over tilde F defined in electron-electron interaction theory are extracted. In the Co- and Cr-doped alloys where the superconducting transition temperatures are raised from that of Ti1-xAlx, we find that the electron-phonon coupli ng, including exchange of virtual phonons, is of crucial importance in determining the value of ($) over tilde F. However, the theory for ($ ) over tilde F in its current form fails to account for our experiment al results. In the Au-doped alloys, the spin-orbit scattering introduc ed by the heavy Au atoms causes a small decrease in the value of ($) o ver tilde F, i.e., ($) over tilde F becomes slightly more negative for higher spin-orbit scattering.