AN ANOMALY IN THE ULTRASONIC ATTENUATION IN STRONG COUPLING AND IMPURE SUPERCONDUCTORS.
Abstract
General expressions for the ultrasonic attenuation response are derived by using a Green's function method. They are sufficiently general to apply to strong coupling superconductors and to superconductors with magnetic impurities. In the appropriate limit the BCS result is obtained. The coefficient of the ultrasonic attenuation consists of two terms; one comes from scattering at frequencies below the effective energy gap, and the other from exciting pairs of quasiparticles from the ground state to above the gap. This second process yields a discontinuity in the coefficient of the ultrasonic attenuation in the superconducting state. The discontinuity vanishes when the singular behaviour in densities of states and of pairs disappears, but its derivative with respect to the temperature has a discontinuity. In the weak coupling limit r becomes one, and the previous result is recovered. Our calculation accounts very well recent experiments of alpha sub S in Al, Hg, and Pb.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 14, 1967
- Accession Number
- AD0663465
Entities
People
- San Boo Nam
Organizations
- Rutgers University–New Brunswick