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Dresden 2003 – scientific programme

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TT: Tiefe Temperaturen

TT 14: Postersitzung III (Neue u. unkonventionelle Supraleiter, Anwendungen der Supraleitung, Dünne Schichten, JJs und SQUIDs, Schwere Fermionen, Kondo-Systeme)

TT 14.9: Poster

Wednesday, March 26, 2003, 14:30–19:00, P2c

Superconducting Sr2RuO4 in an applied magnetic field: A study of the excess current by point-contact spectroscopy — •F. Laube1, G. Goll1, M. Eschrig2, M. Fogelström3, and R. Werner41Physikalisches Institut, Universität Karlsruhe, D-76128 Karlsruhe, Germany — 2Institut für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe, Germany — 3Institute of Theoretical Physics, Chalmers University of Technology and Göteborg University, S-41296 Göteborg, Sweden — 4Institut für Theorie der Kondensierten Materie, Universität Karlsruhe, D-76128 Karlsruhe, Germany

During the last few years Sr2RuO4 has become a prime candidate for an unconventional superconductor with Cooper pairs probably forming a spin-triplet state. We investigated the symmetry of the superconducting order parameter by means of differential conductance dI/dV vs. V measurements of point contacts between Pt and Sr2RuO4 in zero and applied magnetic fields. In the superconducting state an Andreev bound state of zero energy is formed at the superconductor surface which is observed as a zero-bias anomaly in dI/dV vs. V of contacts with a low transmission [1]. Point contacts of high transmission reveal an enhanced dI/dV below V=± Δ/e. In this metallic regime, in contrast to the tunneling limit, excess current occurs. We present results that show a linear dependence of the excess current as a function of temperature and applied magnetic fields over a wide range of the phase diagram. We discuss the observations in the framework of two competing unconventional pairing states, namely the p-wave triplet and the orbital-singlet approach.
[1] F. Laube et al., Phys. Rev. Lett. 84, 1595 (2000).

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