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Ultrasonic attenuation of 700-MHz surface acoustic waves in thin films of superconducting NbN

Journal Article · · Phys. Rev. B: Condens. Matter; (United States)
The temperature dependence of the ultrasonic attenuation of 700-MHz surface acoustic waves has been measured for nine films of superconducting NbN varying in thickness from 0.02 to 0.3 ..mu..m. The films, sputter deposited on LiNbO/sub 3/ substrates, exhibited attenuation changes in the superconducting state which were very similar in each case. These changes did not, however, follow the predictions of Bardeen, Cooper, and Schrieffer. Instead, they began with a sharp decrease for 1 or 2 dB at the transition temperature followed by a leveling off which remained nearly constant until T< or approx. =0.5T/sub c/. It then decreased linearly with temperature until again leveling off below 1.5 K. A tentative explanation is proposed in terms of the Kosterlitz-Thouless vortex-antivortex theory.
Research Organization:
Physics Department, University of Wisconsin, Milwaukee, Wisconsin 53201
OSTI ID:
6095832
Journal Information:
Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 27:5; ISSN PRBMD
Country of Publication:
United States
Language:
English