Signature of antiferromagnetic long-range order in the optical spectrum   of strongly correlated electron systems
  We show how the onset of a non-Slater antiferromagnetic ordering in a correlated material can be detected by optical spectroscopy. Using dynamical mean-field theory we identify two distinctive features: The antiferromagnetic ordering is associated with an enhanced spectral weight above the optical gap, and well separated spin-polaron peaks emerge in the optical spectrum. Both features are indeed observed in LaSrMnO_4 [G\"ossling et al., Phys. Rev. B 77, 035109 (2008)] 
C. Taranto, G. Sangiovanni, K. Held, M. Capone, A. Georges, and A.   Toschi
cond-mat.str-el