Tunneling Properties at the Interface between Superconducting Sr₂RuO₄and a Ru Microinclusion

Abstract

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