Tunneling measurements have been performed on high-quality Ba1-xKxBiO3 single crystals with Tc's between 15 and 30 K. The junctions are Ba1-xKxBiO3/natural barrier/Au sandwich type, which exhibit very low leakage currents at zero bias and sharp conductance peaks at the gap-edges. The average ratio of 2Δ/kBTc = 3.5±0.1 is obtained using more than 20 different junctions (different samples) with TC's determined from tunnel junctions. Temperature dependence of the energy gap is consistent with the BCS prediction. Second derivative measurements of current-voltage characteristics have also been carried out. Observed strengths and peak positions of the superconducting phonon structures in d2I/dV2 strongly support phonon-mediated superconductivity in Ba1-xKxBiO3.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering