Spectroscopic Evidence for Multiple Order Parameter Components in the   Heavy Fermion Superconductor CeCoIn_5
  Point-contact spectroscopy was performed on single crystals of the heavy-fermion superconductor CeCoIn_5 between 150 mK and 2.5 K. A pulsed measurement technique ensured minimal Joule heating over a wide voltage range. The spectra show Andreev-reflection characteristics with multiple structures which depend on junction impedance. Spectral analysis using the generalized Blonder-Tinkham-Klapwijk formalism for d-wave pairing revealed two coexisting order parameter components, with amplitudes Delta_1 = 0.95 +/- 0.15 meV and Delta_2 = 2.4 +/- 0.3 meV, which evolve differently with temperature. Our observations indicate a highly unconventional pairing mechanism, possibly involving multiple bands. 
P. M. C. Rourke (1), M. A. Tanatar (1), C. S. Turel (1), J. Berdeklis   (1), C. Petrovic (2), and J. Y. T. Wei (1) ((1) Univ...