Search for spontaneous edge currents and vortex imaging in Sr2RuO4 mesostructures

Scanning Hall probe microscopy has been used to search for spontaneous fields at the well-defined edges of large mesoscopic disks, etched into the ab surface of very high quality single crystal Sr2RuO4. Such fields are predicted to exist at locations of broken translational symmetry as a consequence of the proposed two-component spin-triplet chiral order parameter (d) over cap = Delta(0)(k(x) +/- ik(y))(z) over cap. We find no evidence for such fields and impose an upper limit of +/-2.5 mG on their magnitude. We do, however, observe an abrupt apparent loss of strong bulk pinning and a change in the screening behavior above H similar to 25 Oe. At high fields (H > 25 Oe) pronounced magnetic screening by the disks is very well described by a model containing only strong edge currents, and bulk critical currents do not appear to play a significant role. Our results are discussed in terms of relevant theoretical predictions.