Edge states of Sr2_2RuO4_4 detected by in-plane tunneling spectroscopy

We perform tunneling spectroscopy of Sr$_2$RuO$_4$ searching for the edge states peculiar to topological superconductivity. Conductance spectra obtained on Sr$_2$RuO$_4$/Au junctions fabricated using $in$ $situ$ process show broad humps indicating the successful detection of a-axis edge of 1.5K phase. Three types of peak shape are detected: domelike peak, split peak and two-step peak. By comparing the experiments with predictions for unconventional superconductivity, these varieties are shown to originate from multiband chiral p-wave symmetry with weak anisotropy of pair amplitude. The broad hump in conductance spectrum is a direct manifestation of the edge state peculiar to the chiral p-wave superconductivity.Comment: 7 pages and 4 figure