Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 23: Posters Superconductivity, Solids at Low Temperature
TT 23.33: Poster
Montag, 7. März 2005, 14:00–18:00, Poster TU D
Investigation of CeCoIn5/Pt point contacts in the normal and superconducting states — •Stefan Kontermann1, Gernot Goll1, Todd Sayles2, and M. Brian Maple2 — 1Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe — 2Institute 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. We report on investigations of CeCoIn5 by point-contact spectrocopy with Pt as the normal-metal counterelectrode. In the normal state a pronounced asymmetry of the differential resistance dV/dI as a function of applied bias V is observed which becomes more pronounced as the temperature is reduced. For a contact in the ballistic regime the asymmetry can be attributed to the emergence of the coherent heavy-fermion liquid. In the superconducting state Andreev reflection of quasiparticles at a normal metal/superconductor interface leads to characteristic minima in the dV/dI vs V spectra. We measured spectra which show either a reduced resistance for bias |V|<Δ/e or a single minimum of dI/dV for V=0, i. e. a zero-bias anomaly. The observation of a zero-bias anomaly is expected only if the order parameter exhibits a sign change as a function of k→ which leads to an Andreev bound state at the surface.