Effect of the energy-dependent density of states on a strong-coupling superconductor

Abstract

The effect of the inclusion of the energy dependence in the electronic density of states (EDOS) on quantities in the superconducting state is studied for strong-coupling superconductors, within the framework of the Eliashberg theory. In order to see how the effect depends on the shape of the EDOS around the Fermi energy when the coupling strength is increased, the critical temperature and the energy gap are calculated with two typical shapes of the Lorentzian EDOS for various electron-phonon coupling strengths. It is shown that the more the coupling strength is increased, the more significantly the energy dependence of the EDOS affects these quantities. The temperature variation of the quasiparticle density of states is calculated for various parameters of the Lorentzian EDOS to examine the temperature dependence of the phonon structures in the tunneling characteristics.