ULTRASONIC DETERMINATION OF THE SUPERCONDUCTING ENERGY GAP IN VANADIUM

Journal Article · Fri Nov 01 04:00:00 EST 1963 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.132.1062· OSTI ID:4697927

Brewster, J L; Levy, M; Rudnick, I

Ultrasonic attenuation measurements on single-crystal cylinders axially oriented along the (110) crystallographic direction were used to determine the temperature-dependent superconducting energy gap 2 epsilon /sub O/T) of three samples of vanadium of different purities. An echo-pulse technique using longitudinal waves was used. The propagation direction was along the (110) for all the experiments. The zerotemperature energy gap for the three samples was found to be (3.4 plus or minus 0.2)kT/sub c/, (3.5 plus or minus 0.2)kT/sub c/ , and (3.5 plus or minus 0.1)kT/sub c/. T hese values were computed by averaging the results obtained from 200 or 300 experimental points. They are in agreement with the Bardeen, Cooper, and Schrieffer result that 2 epsilon /sub O/ ) should be equal to 3.5 kT/sub c/ for all superconductors, The dependence of the normalized energy gap on the reduced temperature of these samples is closely predicted by the BCS theory. These experiments were performed within the frequency range 100 to 450 Mc, and in all of them the product of the ultrasonic wave vector times the electron mean free path was smaller than one. The temperature dependence of the attenuation in the superconducting state showed small oscillations. It is found that the amplitude of these is a small effect for very pure samples. Moreover, evidence was collected to show that these oscillations are not an inherent property of the superconducting state in vanadium but are probably associated with acoustic modes of wave propagation. (auth)

• Research Organization: Univ. of California, Los Angeles
• NSA Number: NSA-17-041622
• OSTI ID: 4697927
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 132; ISSN PHRVA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ABSORPTION
BCS THEORY
CRYSTALS
CYLINDERS
ELECTRONS
ENERGY
ENERGY LEVELS
FREQUENCY
IMPURITIES
LATTICES
MEAN FREE PATH
MEASURED VALUES
MONOCRYSTALS
PHYSICS
PULSES
REFLECTION
SOUND
SUPERCONDUCTIVITY
TEMPERATURE
ULTRASONICS
VANADIUM
VARIATIONS