Two energy gaps in the tunneling-conductance spectra of the superconducting clathrate Ba8Si46

Yves Noat (1) , Tristan Cren (1) , Pierre Toulemonde (2) , Alfonso San Miguel (3) , François Debontridder (1) , Vincent Dubost (1) , Dimitri Roditchev (1)

1 INSP - Institut des Nanosciences de Paris
2 NEEL - MRS - Matériaux, Rayonnements, Structure
3 LPMCN - Laboratoire de Physique de la Matière Condensée et Nanostructures

We have studied the quasiparticle excitation spectrum of the superconductor Ba8Si46 by local tunneling spectroscopy. Using high-energy resolution achieved in superconductor-insulator-superconductor junctions we observed tunneling conductance spectra of a nonconventional shape revealing two distinct energy gaps, ΔL=1.3±0.1 meV and ΔS=0.9±0.2 meV. The analysis of tunneling data identified ΔL as the leading superconducting gap in the bulk material. A smaller and more dispersive gap ΔS is interpreted as induced either in reciprocal space, via the quasiparticle interband scattering from the leading superconducting band, or in real space, by the proximity effect to a normal layer at the surface.

Domaines: Supraconductivité [cond-mat.supr-con]

Yves Noat, Tristan Cren, Pierre Toulemonde, Alfonso San Miguel, François Debontridder, et al.. Two energy gaps in the tunneling-conductance spectra of the superconducting clathrate Ba8Si46. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2010, 81, pp.104522. ⟨10.1103/PhysRevB.81.104522⟩. ⟨hal-00466709⟩