Some effects of an energy dependent electronic density of states on superconductivity

The influence of sharp peaks in the electronic density of states on superconducting properties is studied using the imaginary frequency axis formulation of strong coupling theory suitably generalized to include energy dependence. The critical temperature Tsub(c) and its variation with disorder is calculated for a Lorentzian peak superimposed on a constant background. An analytic continuation of our solutions to the real frequency axis is performed and used to obtain the ratio 2Δsub(O)/ksub(B)Tsub(c) where Δsub(O) is the gap in the quasiparticle excitation spectrum. Tunneling characteristics are calculated and found to be modified by energy dependence. (author)