Field-temperature phase diagram of superconductivity in Sr₂RuO₄-Ru under out-of-plane uniaxial pressure

One of the interesting issues on the spin-triplet superconductor Sr₂RuO₄ (T_c = 1.5 K) is the origin of the T_c enhancement up to about 3 K in the eutectic system Sr₂RuO₄-Ru. We have recently revealed a striking fact that T_c of pure Sr₂RuO₄ is also enhanced up to 3.2 K by uniaxial pressure along the c axis (P_||c). When P_||c is applied to Sr₂RuO₄-Ru, there is a crossover at P^*_||c ~ 0.4 GPa from behavior attributable to interfacial superconductivity (SC) to behavior similar to that in pure Sr₂RuO₄ under P_||c. We focus on the field-temperature phase diagrams of Sr₂RuO₄-Ru above and below P^*_||c. We revealed that the H-T curves of Sr₂RuO₄-Ru both above and below P^*_||c are concave-up. This fact suggests that the P_||c-originated SC above P^*_||c as well as the interfacial SC below P^*_||c are granular-like. We also found that the H-T curves of these SCs do not scale with T_c's, which is possibly related to a difference in the spatial distribution of superconducting regions.