Sound attenuation by helicon modes in high-Tcsuperconductors

The vortex dynamics in a superclean superconductor attains a Hamiltonian form leading to the formation of helicon waves. The latter couple to the transverse sound waves via the electromagnetic interaction as well as via the disorder potential producing vortex pinning. We determine the resonance condition for the driven vortex system and calculate the resulting attenuation of the sound waves. In high-${\mathit{T}}_{\mathit{c}}$ superconductors the helicon modes can be identified via a sharp resonant attenuation of transverse sound.