Electromagnetically Induced Transparency and slow light in media with   Rydberg Excitons
  We show that the Electromagnetically Induced Transparency (EIT) is possible in a medium exhibiting Rydberg excitons and indicate the realistic parameters to perform the experiment. The calculations for a Cu$_2$O crystal are given which show that in this medium due to large group index one could expect slowing down a light pulse by a factor about $10^4$. 
Sylwia Zieli\'nska-Raczy\'nska, David Ziemkiewicz, and Gerard   Czajkowski
quant-ph physics.optics