Optical effects in unmagnetized cold plasmas by a chiral axion factor

Unmagnetized cold plasma modes are investigated in the context of the chiral Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics, where the axion chiral factor acts retrieving some typical properties of magnetized plasmas. The Maxwell equations are rewritten for a cold, uniform, and collisionless fluid plasma model, allowing us to determine the dispersion relation, new refractive indices, and propagating modes. We find four distinct refractive indices modified by the purely timelike CFJ background that plays the magnetic conductivity chiral parameter role associated with right-circularly polarized (RCP) and left-circularly polarized (LCP) waves. For each refractive index, the propagation and absorption zones are determined and illustrated for some specific parameter values. Modified RCP and LCP helicons are found in the low-frequency regime. The optical behavior is investigated, revealing that the chiral factor induces birefringence, measured in terms of the rotatory power (RP). The dichroism coefficient is carried out for the absorbing zones. The negative refraction zones may enhance the involved RP, yielding RP sign reversion, a feature of rotating plasmas and MCFJ chiral plasmas. Charge density oscillations and Langmuir waves are also discussed, revealing no modified dispersion relation due to the chiral axion factor.