Ultrasonic attenuation at 500 kHz in superconducting tin

摘要: The temperature dependence of the longitudinal ultrasonic attenuation in single crystals white tin has been measured by a resonance technique at frequency 500 kHz between 1 and 4.2 $^\circ$K, for propagation along (100) (001). resistance ratio samples varied from 800 to 30 000 all cases electronic mean free path is smaller than wavelength. No difference found (001) most heavily doped samples, contrast suggestion Kadanoff & Pippard, although this case normalized curve lies above form Bardeen, Cooper Schrieffer (B.C.S.). A systematic decrease with increasing purity found, so that pure well below B.C.S. form. This effect more marked propagation. simple model used calculate details elastic scattering anisotropic superconductor, it shown across Fermi surface can account lack any orientational differences. excitations modified anisotropy : brings theory into very good agreement present results, also increases theoretical thermal conductivity as agree experiment. Phonon variation ; consistent gap anisotropy.