Spin-triplet superconducting proximity effect in SrRuO$_{\mathrm{3}}$/Sr$_{\mathrm{2}}$RuO$_{\mathrm{4}}$ hybrids

Spin-\textit{triplet} superconducting correlations can be induced into a ferromagnet (FM) out of a spin-\textit{singlet} superconductor (SSC) via magnetic inhomogeneity at the SSC/FM interface. In this case, however, the proximity effect is not readily controllable because spins are quenched. In contrast, superconducting spintronics can be realized by using spin-\textit{triplet} superconductors (TSCs) and FM hybrids. Theoretically, it has been predicted that spin-triplet proximity effect can be controlled by the relative orientations between the magnetization in the FM and the Cooper pair spin in TSC. We fabricate Au(600-nm)/SrRuO$_{\mathrm{3}}$(15-nm) /Sr$_{\mathrm{2}}$RuO$_{\mathrm{4}}$ junctions by growing epitaxial SrRuO$_{\mathrm{3}}$ FM thin films on Sr$_{\mathrm{2}}$RuO$_{\mathrm{4}}$ TSC single crystals. Differential conductance vs voltage shows the conductance enhancements with superconducting transitions at three different characteristic voltages. These three features can naturally be interpreted as originating from the SC gaps in bulk Sr$_{\mathrm{2}}$RuO$_{\mathrm{4}}$ as well as at two distinct interfaces (Au/SrRuO$_{\mathrm{3}}$ and SrRuO$_{\mathrm{3}}$/Sr$_{\mathrm{2}}$RuO$_{\mathrm{4}})$. The effect of applied magnetic field reveals that the proximity effect is robust against the loss of magnetic inhomogeneity.