Slowing light through Zeeman Coherence Oscillations in a duplicated   two-level system
  We present the theory of a new method to slow a linearly polarized probe pulse as it propagates through a duplicated two-level system driven by an orthogonally polarized control field. The method makes use of Zeeman coherence oscillations (CZO) that arise in the atomic system because of the spatial and temporal modulation of the total polarization. This method exhibits properties similar to those that rely on the electromagnetically induced transparency (EIT) but without the existence of any trapping state. We demonstrated also the propagation of a dark polariton in the medium 
F. A. Hashmi and M. A. Bouchene