P, T -odd Faraday rotation in heavy neutral atoms

Abstract

Accurate evaluation of the $\mathcal{P},\mathcal{T}$-odd Faraday effect (rotation of the polarization plane of the light propagating through a medium in the presence of an external electric field) is presented. The magnitude of this rotation is directly proportional to the optical path length. A novel idea is to observe the $\mathcal{P},\mathcal{T}$-odd Faraday effect using intracavity absorption spectroscopy (ICAS) experiments. The modern ICAS experiments allow one to observe the rotation of the light polarization plane (natural or $\mathcal{P}$-odd) with the optical path length up to a hundred kilometers. This can be done mainly due to the work off-line in the resonance absorption experiments. For the Faraday rotation (ordinary or $\mathcal{P},\mathcal{T}$-odd) the maximum of the effect coincides with the maximum of absorption which usually prevents the work off-line and employment of the large optical path length. However, we propose to use the second rotation maximum that exists for the Faraday effect and would also allow for work off-line. The calculations are performed for the heavy metal atoms Cs, Tl, Pb, and Ra where the $\mathcal{P},\mathcal{T}$-odd effects are most pronounced. The results of the calculations demonstrate that with the large optical path length the ICAS experiments will be able to fix the possible $\mathcal{P},\mathcal{T}$-odd effects at a level comparable with other very advanced modern experiments.