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TT: Tiefe Temperaturen

TT 9: Tunneln und Ordnungsparameter

TT 9.3: Talk

Tuesday, March 27, 2001, 10:00–10:15, H

Point-contact spectroscopy studies on superconducting Sr₂RuO₄: experiment and theory — •F. Laube¹, G. Goll¹, H. v. Löhneysen^1,2, M. Fogelström³, F. Lichtenberg⁴, Z. Q. Mao⁵, and Y. Maeno⁵ — ¹Physikalisches Institut, Universität Karlsruhe — ²Institut für Festkörperphysik, Forschungszentrum Karlsruhe — 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

Sr₂RuO₄, being isostructural to the high T_c superconductor (La,Sr)₂CuO₄, exhibits an unconventional superconducting ground state (T_c=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.

[1] F. Laube et al., Phys. Rev. Lett. 84 (2000) 1595.