Plasmons carrying orbital angular momentum in quantum plasmas

The existence of plasmons with orbital angular momentum due to the Laguerre-Gaussian-type density and potential perturbations is studied in an unmagnetized quantum plasma. Starting from appropriate hydrodynamic equations for the electrostatic electron dynamics, a dispersion equation is derived in paraxial approximation. The Laguerre-Gaussian beam solutions are obtained and the properties of electric field components, energy flux, and corresponding angular momentum density of plasmons are investigated. The electric field lines are found to form helical structures with a dominant axial component. The results are analyzed numerically and the influence of radial and angular mode numbers on potential and electric field components is illustrated.