The Superfluidity and Experimental Properties of Odd-Energy-Gap Superconductors

We consider superconductors with a gap which is an odd function of energy k = ε k - μ, i.e. vanishing everywhere on the Fermi surface; this is done within a BCS framework. Apart from the standard phenomenology (density of states, penetration depth, NMR, C v ( T )), we also look at the stability of the superconducting state. It is stable to finite supercurrents (although with a normal fluid density which increases with the supercurrent density), and a low concentration of non-magnetic impurities affects the low-temperature transport properties very weakly. We find two classes of odd-gap superconductors, which strongly differ in their low-energy properties. For a certain parameter range, most of the results resemble those for d -wave superconductors (except for the effect of impurities).