Twisted ion waves carrying orbital angular momentum in a dense pair-ion plasma

Abstract

Electrostatic ion oscillations carrying finite orbital angular momentum are investigated in an unmagnetized dense quantum degenerate plasma containing electrons, positrons, and ions. Instead of conventional plane wave solutions, Laguerre-Gaussian (LG) type density and potential profiles are considered to solve the wave equation in paraxial approximation. The solutions exhibit finite orbital angular momentum states associated with the ion waves. The electric field structure, energy density, and orbital angular momentum density are theoretically examined. In addition, the numerical analysis is carried out to study the effects of positron concentration on the waves for various radial and angular mode numbers and azimuthal angles. The variation of LG potential and azimuthal field amplitudes with positrons is elaborated. The study has relevance with the possible phonon modes and twisted excitation in dense plasmas in the environment of radiation beams associated with optical vortices or stimulated Brillouin scattering.