Spatial development of superconductivity in the Sr2RuO4-Ru eutectic system

TL;DR

This study investigates the spatial development of enhanced 3-K phase superconductivity in Sr2RuO4-Ru eutectic crystals, revealing anisotropic shielding behavior and the formation of a Josephson network at low temperatures.

Contribution

It provides detailed insights into the anisotropic superconducting shielding and the development of a Josephson network in the Sr2RuO4-Ru eutectic system, clarifying the spatial evolution of the 3-K phase.

Findings

Onset temperature of 3-K phase superconductivity is as high as 3.5 K.

Superconducting shielding is strongly anisotropic, governed by in-plane currents.

Formation of a Josephson network occurs below 2 K, enhancing shielding.

Abstract

We have clarified how the enhanced superconductivity, often referred to as the 3-K phase superconductivity, develops in the Sr2RuO4-Ru eutectic system. From the detailed ac and dc susceptibility measurements on well-characterized crystals, we revealed strongly anisotropic shielding, governed by the direction of the screening current dominated within the RuO2 plane rather than by the orientation of the Ru lamellae. The onset temperature of the 3-K phase superconductivity probed by diamagnetic screening is as high as 3.5 K. The temperature dependence of the diamagnetic shielding above around 2 K is well ascribed by the interfacial screening around each Ru lamella. Below around 2 K, the rapid development of the shielding fraction as well as its peculiar esponse to ac and dc magnetic fields are explained by the formation of the Josephson network consisting of inter-lamellar supercurrents.