ULTRASONIC AND THERMAL EFFECTS IN SUPERCONDUCTORS.
CALIFORNIA UNIV LOS ANGELES DEPT OF PHYSICS
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Some of the properties of three transition metals, niobium, vanadium, and tantalum, were investigated using the ultrasonic technique. The normal attenuation in niobium possessed a typical electron-phonon behavior with a temperature dependence of T to the -3.2 power. In the superconducting state, attenuation was measured in both the absence of a magnetic field and at various values of the external magnetic field. From the ratio of superconducting to normal conducting attenuation, the zero-degree energy gaps of niobium, vanadium, and tantalum were determined. For niobium, an energy gap of 2 delta 0 3.64 plus or minus 0.05 kT sub c was found for the 100 direction of propagation, and an energy gap of 3.70 plus or minus 0.06 kT sub c for the 111 direction. These measurements indicate an anisotropy of the energy gap. The zero-degree energy gap for vanadium was 2 delta 0 3.40 plus or minus 0.07 kT sub c in the 110 direction, and 3.10 plus or minus 0.07 kT sub c for tantalum in the 100 direction. Author
- Electricity and Magnetism