Ultrasonic Attenuation in Normal and Superconducting Indium.
Technical memo. for period ending Aug 80,
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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The dependence of ultrasonic attenuation on temperature, sonic frequency, propagation direction, and superconducting state has been measured in indium single crystals using low-amplitude longitudinal waves. These measurements and the experimental apparatus with which they have been obtained are described. These data indicate that, in addition to the usual electronic attenuation described quantitatively by the BCS theory of superconductivity Bardeen et al., Phys. Rev. 108, 1175, there is an additional source of attenuation. This secondary attenuation is generally attributed to the interaction of sound waves and crystal dislocations within the specimen, a process which has been described most thoroughly by Granato and Lucke J. Appl. Phys. 27, 583. A comparison of the measured dislocation attenuations with those predicted by the theory of Granato and Lucke is given. This theory is shown to be inapplicable to the situation of this experiment, i.e., to indium at low temperatures. Earlier works in which similar data appear to substantiate the Granato and Lucke theory of dislocation attenuation are shown to be insufficient tests of that theory. Author
- Solid State Physics