ENHANCEMENT OF BROKEN-TIME-REVERSAL-SYMMETRY PAIRING STATE IN D-WAVE SUPERCONDUCTORS WITH NONMAGNETIC IMPURITIES

The phase diagrams of a superconductor with dominant d-wave and minor s-wave pairing interactions are obtained with the self-consistent gap equations. A possible broken-time-reversal-symmetry s+id state in an a ppropriate interaction/temperature range is shown. We point out that a minor s-wave pairing interaction normally cannot compete with the dom inant d-wave pairing so that the bulk state usually has a pure d-wave symmetry. Moreover, we show that the possibility to observe the s+ id stale in a bulk system can be enhanced greatly if nonmagnetic impurity scatterings are introduced. Also interestingly, the amplitude of d-wa ve order parameter in the s+id phase is shown to decrease with lowerin g temperature.