Andreev reflection in heavy-fermion superconductors and order parameter symmetry in CeCoIn5.
Differential conductance spectra are obtained from nanoscale junctions on the heavy-fermion superconductor CeCoIn5 along three major crystallographic orientations. Consistency and reproducibility of characteristic features among the junctions ensure their spectroscopic nature. All junctions show a similar conductance asymmetry and Andreev reflectionlike conductance with a reduced signal ( approximately 10%-13%), both commonly observed in heavy-fermion superconductor junctions. Analysis using the extended Blonder-Tinkham-Klapwijk model indicates that our data provide the first spectroscopic evidence for d_{x;{2}-y;{2}} symmetry. To quantify our conductance spectra, we propose a model by considering the general phenomenology in heavy fermions, the two-fluid behavior, and an energy-dependent density of states. Our model fits to the experimental data remarkably well and should invigorate further investigations.
Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
W K
WK
Park
J L
JL
Sarrao
J D
JD
Thompson
L H
LH
Greene