Theory of novel properties of Josephson effect in anisotropic superconductors

Recent studies on high-Tc superconductors aroused our new interest on the Josephson effects in anisotropic superconductors. In contrast to the conventional s-wave superconductors, there are two additional intrinsic effects originating from an internal phase of the pair potential. One is the sign change of the Josephson current depending on the direction of the motion of the Cooper pair. The other is the formation of localized states near the insulator. By taking account of these two effects, a general formula for the Josephson current is presented. Calculated results predict several anomalous properties including a strong enhancement of the Josephson current at low temperature. The influences of the spatial dependence of the pair potential on the Josephson current are also clarified.