Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion SuperconductorCeCoIn5

Abstract

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.

Correlation-drivend-wave superconductivity in Anderson lattice model: Two gaps

“…We obtain a nodal pairing with the two distinct gaps at the Fermi surface, in accord with the findings for CeCoIn 5 [5,[40][41][42]. In the Fig.…”

“…In this manner, the appearance of the superconducting pairing is proved as solely due to the electron correlations within one of the most representative methods of treating the correlated model systems. Such SC state reflects the principal features exhibited by the canonical, quasi-two-dimensional [26,27] HFS CeCoIn 5 , for which the signatures of the nodal [28][29][30][31][32][33] [5,[34][35][36][37][38][39][40][41][42] SC of multigap character [5,[40][41][42] were reported. Moreover, as in our approach the leading SC component emerges from f electrons, which are also responsible for the magnetic properties in HFS, our model accounts in a natural manner for the common origin of magnetic and SC orderings [43].…”

Strong Anisotropy in Spin Susceptibility of Superfluid3He-B Film Caused by Surface Bound States

“…For example, the zero-bias conductance peak (ZBCP) in the tunneling spectrum of high T c superconductors [4][5][6] has been ascribed to the zero-energy bound states. ZBCP has been also observed in other superconductors, such as Sr 2 RuO 4 , 7) -(BEDT-TTF) 2 Cu[N(CN) 2 ]Br, 8) UBe 13 , 9) and CeCoIn 5 , 10) and was regarded as evidence of their unconventionality. The surface bound states in p-wave pairing superfluid 3 He 1,2,11-13) have not been observed until recently, because of the lack of an appropriate probe for the neutral superfluid.…”

Unconventional Andreev reflection on the quasi-one-dimensional superconductor Nb2PdxSe5

“…To the best of our knowledge, a 2∆/k B T C ratio greater than 20 has only been previously reported in the heavy fermion superconductor CeCoIn 5 . 28 In CeCoIn 5 , the large gap-to-T C ratio is attributed to an enhancement through interband coupling and is regarded as a signature of an unconventional pairing mechanism in the heavy fermion superconductor. In the case of Nb 2 Pd x Se 5 , given the fact that the material has a complex fermi surface consisting of three electron and hole bands, 6 the pairing of electrons between different bands may also follow an unconventional mechanism, thus resulting in a substantially enhanced gap.…”