Inhomogeneous excited states in superconductors

Abstract

We investigate a new inhomogeneous excited state in superconductors in the absence of external fields and interface effects. We find that for the one-dimensional system this state has an energy less than the Bardeen-Cooper-Schrieffer gap, Δ, for a range of coherence length. Such states might be found in quasi-one-dimensional organic superconductors and in systems with planar nested Fermi surfaces, such as the ceramic oxides. In higher than one dimension the energy of this state is greater than Δ unless Δ is at least comparable to the Fermi energy.