Exchange effects in Coulomb quantum plasmas: Dispersion of waves in 2D and 3D quantum plasmas

Abstract

We describe quantum hydrodynamic equations with the Coulomb exchange interaction for three and two dimensional plasmas. Explicit form of the force densities are derived. We present non-linear Schrödinger equations (NLSEs) for the Coulomb quantum plasmas with the exchange interaction. We show contribution of the exchange interaction in the dispersion of the Langmuir, and ion-acoustic waves. We consider influence of the spin polarization ratio on strength of the Coulomb exchange interaction. This is important since exchange interaction between particles with same spin direction and particles with opposite spin directions are different. At small particle concentrations n0≪1025cm−3 and small polarization the exchange interaction gives small decrease of the Fermi pressure. With increase of polarization role the exchange interaction becomes more important, so that it can overcome the Fermi pressure. The exchange interaction also decreases contribution of the Langmuir frequency. Ion-acoustic waves do not exist in limit of large polarization since the exchange interaction changes the sign of pressure. At large particle concentrations n0≫1025cm−3 the Fermi pressure prevails over the exchange interaction for all polarizations. We obtain a similar picture for two dimensional quantum plasmas.