Enhancement of broken-time-reversal-symmetry pairing state in-wave superconductors with nonmagnetic impurities

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