Superconducting energy gap in (Formula presented) has been investigated using a break-junction tunneling technique. The observed differential conductance (Formula presented) is well described by the BCS density of states with a small lifetime broadening parameter. We have found small gap values for the local low-(Formula presented) phases in addition to the bulk (Formula presented) of 15.6-16.6 K. The gap value of (Formula presented) meV with (Formula presented) K gives the BCS ratio of (Formula presented), which is kept constant down to the observed lowest (Formula presented) of 4.6 K. These results give clear evidence for the BCS mechanism of superconductivity for these compounds.
|Number of pages||10|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Jan 1 1996|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics