Heavy electron superconductors

Abstract

We use group theory to classify p-wave superconducting states in cubic, hexagonal, and tetragonal crystals with spin-orbit coupling. In some superconducting phases belonging to multidimensional irreducible representations, time reversal symmetry is broken. In such cases a Josephson current may flow through a contact with an ordinary s-wave superconductor. The modulus of the gap function vanishes at symmetry points in some phases but never on a line. The effect of normal impurities is also studied. A finite density of impurities is required to give a finite density of states at the Fermi energy if the gap vanishes at points but an infinite-simal density would suffice in any state with lines of zeros.