Tunneling. cap alpha. /sup 2/F(. omega. ) and heat-capacity measurements in high-T/sub c/ Nb/sub 3/Ge
Improved film synthesis has allowed us to prepare Nb/sub 3/Ge/SiO/sub x//Pb tunnel junctions on samples with high T/sub c/ (up to 21.2 K) and large energy gap (..delta..3Ge up to 3.85 meV). 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. The trend previously seen of a movement of the lowest phonon branch to lower energies as the T/sub c/ and gap increase is continued, resulting in the lowest-energy phonon mode being well defined and enhanced in strength. Theoretical functional derivatives for T/sub c/ (by Bergmann and Rainer) and the energy gap (by Mitrovic et al.) qualitatively explain the rise in T/sub c/, energy gap, and 2..delta../k/sub B/T/sub c/. Heat-capacity measurements have been performed on various samples to give bulk Nb/sub 3/Ge properties, including one sample which was analyzed by tunneling ..cap alpha../sup 2/F(..omega..) and heat capacity. ..gamma.. = 34 +- 1.5 mJ/mole K/sup 2/ and the bare density of states, N(0) = 1.5 +- 0.1 states/eV atom, suggests that a high density of states is inadequate to explain the high T/sub c/ in Nb/sub 3/Ge. Values for 2..delta../k/sub B/T/sub c/ = 4.2 +- 0.1 and ..delta..C/..gamma..T/sub c/approx.1.9 indicate a strong-coupled superconductor, in agreement with tunneling results on this sample.
- Research Organization:
- Code 6634 Naval Research Laboratories, Washington, D.C. 20375
- OSTI ID:
- 5154583
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Journal Issue: 1 Vol. 29:1; ISSN PRBMD
- Country of Publication:
- United States
- Language:
- English
Similar Records
Tunneling. cap alpha. /sup 2/F(. omega. ) as a function of composition in A15 V-Si
Proximity electron tunneling spectroscopy. III. Electron-Phonon coupling in the Nb-Zr system
Related Subjects
360104* -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHALCOGENIDES
DATA
DEPOSITION
ELEMENTS
ENERGY BEAM DEPOSITION
ENERGY GAP
ENERGY-LEVEL DENSITY
EXPERIMENTAL DATA
FILMS
GERMANIUM COMPOUNDS
HIGH VACUUM
INFORMATION
JUNCTIONS
LEAD
MATHEMATICAL MODELS
METALS
NIOBIUM COMPOUNDS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PARTICLE MODELS
PHONONS
PHYSICAL PROPERTIES
QUASI PARTICLES
SILICON COMPOUNDS
SILICON OXIDES
SPECIFIC HEAT
STRONG-COUPLING MODEL
SUPERCONDUCTING JUNCTIONS
SURFACE COATING
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
TUNNEL EFFECT