Cutoff parameter versus Ginzburg-Landau coherence length in the mixed state of high-κ superconductors with impurities: quasiclassical approach

The influence of the impurities on the ratio of the cutoff parameter, xi(h), and the Ginzburg-Landau coherence length, xi(c2), in the mixed state of high-kappa s-wave superconductors is investigated in framework of the quasiclassical nonlocal Eilenberger theory. Quasiparticle scattering by impurities and lowering of the temperature reduce the value of xi(h) to values much less than xi(c2). This is different from the prediction of the local Ginzburg-Landau theory where xi(h) is scaled by xi(c2). Detailed comparison with the behavior of the order parameter coherence length xi(1) is done. It is found that impurities influence by different way on xi(h) and xi(1). The curve xi(h)/xi(c2) (B/B-c2) shifts downward with increasing of impurity scattering rate while xi(1)/xi(c2) (B/B-c2) curve shifts upward in this case.