Andreev reflection in heavy-fermion superconductors and order parameter symmetry in CeCoIn5

• Published in: Physical review letters Vol. 100; no. 17; p. 177001
• Main Authors: Park, W K, Sarrao, J L, Thompson, J D, Greene, L H
• Format: Journal Article
• Language: English
• Published: United States 02-05-2008
• ISSN: 0031-9007
• DOI: 10.1103/PhysRevLett.100.177001

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.