<p> It is believed that Sr2RuO4 is a triplet superconductor that breaks time reversal symmetry, and it is expected to have spontaneous magnetization both at the sample edge, as well as at domain walls. Recent magnetic microscopy results place upper limits on the magnetic fields differing from previous theoretical calculations by 2 orders of magnitude. Using a Ginzburg-Landau formalism we investigate the effects of a rough surface as well as parameter choices which differ from the typical weak coupling parameters on the magnitudes of the spontaneous supercurrents and magnetic fields. The dependance on surface roughness is found to be small resulting in only a 20% reduction for the weak coupling parameters. Changing the parameters from weak coupling in addition to pair breaking surface effects is also found to affect the magnitudes of the spontaneous fields weakly, except in certain unphysical parameter regimes. The effects of the surface stabilizing another non-magnetic order parameter are considered, and give rise to field distributions with similar features to those present at domain walls.</p> / Thesis / Master of Science (MSc)

In this thesis we study the edge currents and the multi-band superconductivity in the unconventional superconductor Sr2RuO4. Numerous measurements have given strong support for a topologically non-trivial time-reversal symmetry breaking chiral p-wave state in this material. However, the spontaneous edge current expected for this order has eluded experimental detection. In this thesis, we present a general theoretical description of the edge currents in chiral superconductors. Our results elucidate the connection between the edge currents and the topological property of the chiral pairing. On this basis, we argue that superconducting gap anisotropy, combined with surface disorder, may provide an explanation for the absence of observable edge currents in Sr2RuO4. In addition, contrary to intuitive expectations, the integrated edge current is found to identically vanish for any non-p-wave chiral superconductor in the continuum limit-- a result which may be connected with the orbital angular momentum problem in chiral superfluids, such as the A phase of He-3. In lattice models, the integrated edge current may not vanish in non-p-wave superconductors but, in general, is substantially smaller compared to that of a simple chiral p-wave. In a separate study, we investigate the multi-band nature of the superconductivity in Sr2RuO4, via explicit microscopic calculations of the multi-band interactions. Our results indicate comparable pairing correlations on all of the bands and the existence of soft collective phase fluctuations--a Leggett mode. We also examine the possibility of alternative time-reversal symmetry breaking multi-band superconductivity which does not necessarily require chiral p-wave pairing. / Thesis / Doctor of Philosophy (PhD)