We present direct imaging of magnetic flux structures in the anisotropic, spin-triplet superconductor Sr$_{ 2}$RuO$_{ 4}$ using a scanning $\mu$SQUID microscope. Individual quantized vortices were seen at low magnetic fields. Coalescing vortices forming flux domains were revealed at intermediate fields. Based on our observations we suggest that a mechanism intrinsic to the material stabilizes the flux domains against the repulsive vortex-vortex interaction. Topological defects like domain walls can provide this, implying proof for unconventional chiral superconductivity.
Categories: cond-mat.supr-con