Numerical study of unconventional superconductor/a quantum dot/unconventional superconductor junction

A numerical study on the Josephson current through a quantum dot has been done by means of the quantum Monte Carlo method. We consider a dot which contacts to two gapless superconductors with d-wave pairing or p-wave pairing to enhance the possible Kondo effect at low temperatures. The junction becomes a π junction caused by the Coulomb blockade in a temperature range depending on strength of the repulsion U on the dot. Our result on temperature dependence of the current shows that the current through the π junction is suppressed by decreasing the temperature, when the zero energy states enhance the Kondo effect.