Dynamical Superconducting Order Parameter Domains in Sr sub(2)RuO sub(4)

We present direct evidence for complex p-wave order parameter symmetry and the presence of dynamical chiral order parameter domains of the form p sub(x) c ip sub(y) in the ruthenate superconductor Sr sub(2)RuO sub(4). The domain structure creates differences in the magnetic field modulation of the critical current of Josephson junctions fabricated on orthogonal faces of Sr sub(2)RuO sub(4) single crystals. Transitions between the chiral states of a domain or the motion of domain walls separating them generates telegraph noise in the critical current as a function of magnetic field or time and is responsible for hysteresis observed in field sweeps of the critical current. The presence of such domains confirms the p-wave triplet spin and complex (broken time-reversal symmetry) nature of the superconducting pairing state in Sr sub(2)RuO sub(4).