Effects of impurities on superconductivity in noncentrosymmetric compounds

We microscopically derive the Ginzburg-Landau free-energy functional for a noncentrosymmetric superconductor with a large spin-orbit splitting of the electron bands, in the presence of nonmagnetic impurities. The critical temperature is found to be suppressed by disorder, both for conventional and unconventional pairings, in the latter case according to the universal Abrikosov-Gor’kov function. The impurity effect on the upper critical field turns out to be nonuniversal, determined by the pairing symmetry and the band structure. In a BCS-like model, T_c is not affected, while H_c2 increases with disorder. For unconventional pairing, both T_c and H_c2 are suppressed by disorder.