Point-contact spectroscopy studies on superconducting Sr2RuO4: experiment and theory

F. Laube1, G. Goll1, H. v. Löhneysen1,2, M. Fogelström3, F. Lichtenberg4, Z. Q. Mao5 und Y. Maeno5
3Institute of Theoretical Physics, Chalmers University of Technology and Göteborg University, Sweden
4Experimentalphysik VI, Elektronische Korrelationen und Magnetismus, Institut für Physik, Universität Augsburg
5Department of Physics, Kyoto University, Japan
1Physikalisches Institut, Universität Karlsruhe
2Institut für Festkörperphysik, Forschungszentrum Karlsruhe

Sr2RuO4, being isostructural to the high Tc superconductor (La,Sr)2CuO4, exhibits an unconventional superconducting ground state (Tc = 1.5 K). We present conductance measurements of normal conductor/superconductor point-contacts between Pt and Sr2RuO4 in zero and applied magnetic field in order to get information about the symmetry of the superconducting order parameter. In the superconducting state an Andreev bound state is formed at the superconductor surface, which is observed as a zero-bias anomaly in the spectra, i.e. dI/dV vs. V [1]. We compare measurements on different single-crystals with theoretical predictions within a self-consistent quasiclassical approach - possible up to the thermodynamic critical field - and conclude that a spin-triplet state is most favourable.