Twisted positron-acoustic wave in quantum plasmas

In this paper, we explore the existence of positron-acoustic wave (PAW) carrying orbital angular momentum (OAM) in a quantum electron-positron-ion (EPI) plasma system containing electrons, two-temperature positrons, and immobile ions as a neutralizing background. To achieve this aim, we employ the quantum hydrodynamic approach to obtain the evaluation equation of cold positrons density. By solving this equation in the paraxial limit, the Laguerre–Gaussian (LG) modes of positron perturbation are derived, and their corresponding angular momentum densities are calculated. In the following, based on numerical analyses it is found that the evolution of LG potentials and cold positrons density oscillations are greatly affected by variation of radial and angular mode numbers, relative Fermi temperature of hot species, positrons concentration, and azimuthal phase value. It is expected that the results of this study will give more insight into the positrons dynamics in dense astrophysical and laboratory plasmas. (paper)