Theory ofHc2for superconductors with energy-dependent electronic density of states

A model dispersion relation is developed which describes a peak structure in the electronic density of states near or at the Fermi energy. With the use of this model, the normal-state electron Green's function is calculated in its configuration-space representation. On the basis of strong-coupling theory an eigenvalue equation is derived which determines $H_{c2}$ of a superconducting alloy with a peak structure in the electronic density of states. The results of this eigenvalue equation are discussed analytically for small peak structures and in the weak-coupling limit of the Eliashberg theory.