Tunneling properties at the interface between superconducting Sr2RuO4 and a Ru micro-inclusion

TL;DR

This study investigates the tunneling spectra at the interface between superconducting Sr2RuO4 and Ru micro-inclusions, revealing Andreev bound states and their dependence on temperature and magnetic field, supporting a single-component superconducting state.

Contribution

It provides direct tunneling measurements at the Sr2RuO4-Ru interface, demonstrating the presence of Andreev bound states and supporting a specific superconducting pairing symmetry.

Findings

Zero bias conductance peak observed at the interface.

ZBCP appears below the superconducting transition temperature.

Onset magnetic field of ZBCP is smaller than the upper critical field.

Abstract

We have investigated the magnetic field and temperature dependence of the tunneling spectra of the eutectic system Sr2RuO4-Ru. Electric contacts to individual Ru lamellae embedded in Sr2RuO4 enable the tunneling spectra at the interface between ruthenate and a Ru microinclusion to be measured. A zero bias conductance peak (ZBCP) was observed in the bias voltage dependence of the differential conductance, suggesting that Andreev bound states are present at the interface. The ZBCP starts to appear at a temperature well below the superconducting transition temperature. The onset magnetic field of the ZBCP is also considerably smaller than the upper critical field when the magnetic field is parallel to the ab-plane. We propose that the difference between the onset of the ZBCP and the onset of superconductivity can be understood in terms of the existence of the single-component state predicted by Sigrist and Monien.