Large Enhancement of 3-K Phase Superconductivity in the Sr₂RuO₄–Ru Eutectic System by Uniaxial Pressure

Abstract

While the superconducting transition temperature T_c of Sr₂RuO₄ is 1.5 K, its onset T_c is enhanced as high as 3 K in the Sr₂RuO₄–Ru eutectic system, which is often referred to as the 3-K phase. We have investigated effects of uniaxial pressure on the non-bulk superconductivity in the 3-K phase. While T_c of pure Sr₂RuO₄ is known to be suppressed by hydrostatic pressure, a large enhancement of the superconducting volume fraction of the 3-K phase was observed for both out-of-plane and in-plane uniaxial pressures. Especially, under the in-plane pressure, the shielding fraction at 1.8 K of only less than 0.5% at 0 GPa exceeds 40% at 0.4 GPa. Such a large shielding fraction suggests that under the uniaxial pressure interfacial 3-K phase superconductivity penetrates deep into the bulk of Sr₂RuO₄. The present finding provides a significant implication to the unresolved origin of the enhancement of T_c to 3 K in the Sr₂RuO₄–Ru eutectic system.