Tunneling. cap alpha. /sup 2/F(. omega. ) as a function of composition in A15 NbGe
We have fabricated high-quality A15 NbGe-SiO/sub x/-Pb tunnel junctions on electron-beam-codeposited oxygen-doped Nb/sub 3/Ge. 2..delta../k/sub B/T/sub c/ rises from the Bardeen-Cooper-Schrieffer limit in Ge-poor samples to become strong coupled (2..delta../k/sub B/T/sub c/approx.4.35) as stoichiometry is approached. These junctions have satisfactory features for taking derivative measurements. The data were reduced by the modified McMillan-Rowell proximity-gap inversion analysis developed by Arnold and Wolf to generate ..cap alpha../sup 2/F(..omega..) and related microscopic parameters. As the T/sub c/ and gap increase, a movement of the lowest phonon branch to lower energies is observed with a resultant decrease in <..omega../sup 2/>. The lambda increases with T/sub c/ while <..omega../sup 2/> decreases, in agreement with the idea that mode softening is a major factor in the increase of T/sub c/ with approach to stoichiometry, as previously found in Nb/sub 3/Al by Kwo and Geballe.
- Research Organization:
- Department of Applied Physics, Stanford University, Stanford, California 94305
- OSTI ID:
- 6024632
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 24:7; ISSN PRBMD
- Country of Publication:
- United States
- Language:
- English
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SUPERCONDUCTIVITY AND SUPERFLUIDITY
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