Topological competition of superconductivity in Pb/Ru/Sr_2RuO_4 junctions

Abstract: We devise a new proximity junction configuration where an s-wave superconductivity and the superconductivity of Sr2RuO4 interfere with each other. We reproducibly observe in such a Pb/Ru/Sr2RuO4 junction with a single Pb electrode that the critical current Ic drops sharply just below the bulk Tc of Sr2RuO4 and furthermore increases again below a certain temperature below Tc. In order to explain this extraordinary temperature dependence of Ic, we propose a competition effect involving topologically distinct superconducting phases around Ru inclusions. Thus, such a device may be called a "topological superconducting junction".