Nonlinear absorption of sound in gallium in the superconducting state
Fil' V.D. , Denisenko V.L , Bezuglyi P.A.
Singularities in the behavior of absorption and velocity sound were observed in the region of the superconducting state near Tc under conditions when the sample was acted upon by an additional high-power ultrasonic field. These singularities seem to indicate a restructuring of the energy spectrum of the superconductor.