Phonons with orbital angular momentum in ultrarelativistic dense plasmas

Studying phonon modes with orbital angular momentum (OAM) in ultra-relativistic dense plasmas provides new insights into wave dynamics under extreme conditions. This work investigates the excitation and propagation of phonon modes with OAM in a fully degenerate plasma characterized by inertialess ultra-relativistic degenerate electrons and nondegenerate inertial ions. The fluid theory yields a paraxial wave equation governing the ion density perturbations that admit solutions in the form of Laguerre–Gaussian (LG) beams. These solutions reveal that LG phonon modes possess finite OAM, analogous to twisted light beams in optics. We analyze the electric field components, the angular momentum density, and the energy flux associated with these modes, demonstrating their dependence on key parameters, including the azimuthal angle, beam waist, and electron number density. We explore the implications of OAM transfer in ultra-relativistic dense plasmas, highlighting its potential role in energy transport and wave–particle interactions.