Theory of ultrafast quasiparticle dynamics in high-temperature   superconductors: Pump fluence dependence
  We present a theory for the time-resolved optical spectroscopy of high-temperature superconductors at high excitation densities with strongly anisotropic electron-phonon coupling. A signature of the strong coupling between the out-of-plane, out-of-phase O buckling mode ($B_{1g}$) and electronic states near the antinode is observed as a higher-energy peak in the time-resolved optical conductivity and Raman spectra, while no evidence of the strong coupling between the in-plane Cu-O breathing mode and nodal electronic states is observed. More interestingly, it is observed that under appropriate conditions of pump fluence, this signature exhibits a re-entrant behavior with time delay, following the fate of the superconducting condensate. 
Jianmin Tao, Rohit P. Prasankumar, Elbert E. M. Chia, Antoinette J.   Taylor, Jian-Xin Zhu
cond-mat.supr-con