Phonon-induced electron-electron interaction in disordered superconductors

Abstract

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 F̃ 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 F̃. However, the theory for F̃ 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 F̃, i.e., F̃ becomes slightly more negative for higher spin-orbit scattering.

Source-reported materials — not catalogue approval

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