Ultrasonic investigation of gallium superconducting properties

The superconducting energy gap of gallium has been determined along the three principal crystallographic axes from the temperature dependence of the attenuation of longitudinal ultrasonic waves with frequencies in the range 10 to 150 MHz. Like many other physical properties of gallium, the gap was found to be highly anisotropic. A self-consistent method was developed and used in order to determine the part of ultrasonic attenuation caused by electron-phonon interactions. An abnormal peak of attenuation, for which no explanation can be given, was observed for propagation along b axis. Finally, the investigation of transition temperature against magnetic field has allowed the discontinuity of specific heat at the critical temperature to be estimated. (author)