Microscopic view on the ultrafast photoluminescence from photo-excited   graphene
  We present a joint theory-experiment study on ultrafast photoluminescence from photoexcited graphene. Based on a microscopic theory, we reveal two distinct mechanisms behind the occurring photoluminescence: Besides the well-known incoherent contribution driven by non-equilibrium carrier occupations, we found a coherent part that spectrally shifts with the excitation energy. In our experiments, we demonstrate for the first time the predicted appearance and spectral shift of the coherent photoluminescence. 
Torben Winzer, Richard Ciesielski, Matthias Handloser, Alberto Comin,   Achim Hartschuh, and Ermin Malic
cond-mat.mes-hall