Solitons Formed by Dark-State Polaritons in Electromagnetic Induced   Transparency
  We show the possible stable soliton generation for the dark-state polaritons (DSPs) in an electromagnetic induced transparency (EIT) medium composed of $\Lambda$-type atoms. Whether the solitons are dark or bright can be controlled by the coupling field intensity and the one photon detuning of the probe field. Besides, the velocity and time width of the solitons also can be adjusted by the coupling light. 
Xiong-Jun Liu, Hui Jing and Mo-Lin Ge