Dynamical Superconducting Order Parameter Domains in Sr2RuO4

We present direct evidence for complex p-wave order parameter symmetry and the presence of dynamical chiral order parameter domains of the form p x ± ip y in the ruthenate superconductor Sr 2 RuO 4 . The domain structure creates differences in the magnetic field modulation of the critical current of Josephson junctions fabricated on orthogonal faces of Sr 2 RuO 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 2 RuO 4 .