Optical effects in an electric dipole spin polarized relativistic quantum plasma

Abstract

The covariant, spin-dependent response tensor for an electric dipole-moment-polarized electron gas (statistical distribution of electrons and positrons) is calculated using the formalism of quantum plasmadynamics. A simultaneous eigenfunction of both the Dirac Hamiltonian and the electric moment spin operator is constructed. Expressions for the electric moment states and the corresponding vertex functions are derived. It is shown that when the distribution of momenta is isotropic, the spin-dependent response of an electric-moment-dependent quantum plasma is identically zero. The response is nonzero in the presence of a streaming motion perpendicular to the axis if the electron and positron distributions are different. The response has the same form as for a plasma with a nonzero, cross field current when ⟨pi⟩≠0. This quantum relativistic correction is used to identify the dispersion equation for an electric moment spin-polarized plasma with a streaming cold plasma background. In particular, the natural modes of an electric-moment-dependent quantum plasma exhibit elliptical polarization. This is in contrast to a magnetic-moment-dependent electron gas, which is gyrotropic, or a helicity-dependent electron gas, which is optically active. The different responses, due to quantum plasmas being spin-polarized by different relativistically acceptable spin operators, does not appear in other approaches to quantum plasma theory. Published by the American Physical Society 2025