Effects of incomplete superconducting condensation in S-wave superconductors

We have reexamined quasiparticle excitations in s-wave superconductors by considering a finite range T-d of pairing interaction energy. When T-d is finite, low-energy states which are believed to be a hallmark of other pairing symmetries such as d-wave symmetry are also found in s-wave superconductors. We have numerically computed (i) the quasiparticle density of states, (ii) the order parameter, (iii) the superfluid density as a function of T-d/T-c, and (iv) the critical temperature T-c as a function of effective coupling constant. These calculations show unusual features which arise as a result of these low-energy states when T-d becomes comparable to T-c. In conventional superconductors, where T-d/T(c)much greater than 1, the BCS results are recovered as the effect of the low-energy states becomes negligible.