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. Werner4 — 1Physikalisches 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).