We show how a medium, under the influence of a coherent control field that is resonant or close to resonance to an appropriate atomic transition, can lead to very strong asymmetries in the propagation of unpolarized light when the direction of the magnetic field is reversed. We show how electromagnetically induced transparency (EIT) can be used in atomic vapor to mimic this magnetochiral effect that occurs in natural systems. EIT can produce much larger asymmetry than the well-known magnetochiral effect as we use the dipole-allowed transitions here. Using density-matrix calculations we present results for the breakdown of the magnetic-field-reversal symmetry for two different atomic configurations.
The effect of incident light field ellipticity on the electromagnetically induced absorption (EIA) and electromagnetically induced transparency (EIT) resonances has been studied experimentally and computationally in Hanle configuration with longitudinal and transverse magnetic fields. We identify the Zeeman coherences that influence the resonance profile and study the role of coherence-transfer from excited to ground state via spontaneous emission as a function of ellipticity for the ${F}_{g}=2\ensuremath{\rightarrow}{F}_{e}=3$ transition of
87Rb. The EIT resonance observed with the light field locked on the ${F}_{g}=1\ensuremath{\rightarrow}{F}_{e}=2$ transition of
87Rb is an influence of the nearby ${F}_{g}=1\ensuremath{\rightarrow}{F}_{e}=0$ closed and ${F}_{g}=1\ensuremath{\rightarrow}{F}_{e}=1$ open transitions. With increase in ellipticity the observed EIA and EIT resonances diminish in amplitude for a longitudinal magnetic field and are enhanced for a transverse magnetic field. We computationally account for these observations and discuss the factors that influence the EIA and EIT resonance amplitudes as a function of ellipticity and show that for a transverse field scan the ellipticity dependence of the EIA resonance amplitude can be accounted for without invoking the Doppler effect unlike for a longitudinal field scan. We also show that the maximum in the EIA resonance amplitude obtained for nonzero ellipticities with a longitudinal magnetic field depends on the closedness of the atomic system.