Regensburg 2002 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 9: Neue und unkonventionelle Supraleiter I
TT 9.6: Vortrag
Dienstag, 12. März 2002, 10:45–11:00, H19
Possible unconventional superconductivity in CeCoIn5 probed by point-contact spectroscopy — •Gernot Goll1, Hilbert v. Löhneysen1,2, Vivien S. Zapf3, Eric D. Bauer3, and M. Brian Maple3 — 1Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe — 2Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe — 3Institute for Pure and Applied Physical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
The ternary rare-earth compound CeCoIn5 becomes superconducting for temperatures T≤ 2.3 K, the highest transition temperature among the heavy-fermion superconductors. Power-law behavior of the specific heat and the thermal conductivity in the superconducting state give evidence that the superconductivity in this material is unconventional [1]. We report on investigations of CeCoIn5 by point-contact spectrocopy with Pt as the normal-metal counterelectrode. Andreev reflection of quasiparticles at a normal metal/superconductor interface leads to characteristic features in the differential conductance dI/dV as a function of applied bias V. We measured spectra which show either an enhanced conductance for bias |V|<Δ/e or a single maximum of dI/dV for V=0, i. e. a zero-bias anomaly, depending on the transparency of the interface barrier. The observation of a zero-bias conductance anomaly is expected only if the order parameter exhibits a sign change as a function of k→ which leads to a bound state at the surface. Therefore the data support possible unconventional superconductivity in CeCoIn5. Different order-parameter scenarios will be discussed.
[1] R. Movshovich et al., Phys. Rev. Lett. 86, 5152 (2001).