Tc calculation of disordered superconductor with local electron pairing

Authors:

• G Litak,
• K.I Wysokiński,
• Roman Micnas,
• Stanisław Robaszkiewicz

Abstract

Starting with an effective hamiltonian describing a disordered substitutional alloy superconductor with local electron pairing, we derive a random version of the Gorkov equations in the weak coupling limit. The disorder is treated by means of the coherent potential approximation. We take special care of the energy dependence of the order parameter as introduced by averaging. This leads to a complex wave function renormalisation parameter Z similar to that found in strong coupling theory. The transition temperature T_c is calculated analytically for the lorentzian density of states of the host metal. The numerical calculation of T_c has been performed for a range of phenomenologically important parameters such as alloy concentration, relative position of (random) atomic levels, value of on-site effective attraction and carrier density for the densities of states suitable for d=2 and d=3 spatial dimensions and bipartite lattices. © 1992.