Evidence for a photoinduced nonthermal superconducting-to-normal-state phase transition in overdoped Bi2Sr2Ca0.92Y0.08Cu2O8+δ

Here we report extensive ultrafast time-resolved reflectivity experiments on overdoped Bi2Sr2Ca1-xYxCu2O8+delta single crystals (T-c = 78 K) aimed to clarify the nature of the superconducting-to-normal-state photoinduced phase transition. The data show a lack of the quasiparticle decay time divergence at the fluence required to induce this phase transition, in contrast to the thermally driven phase transition observed at T-c and at variance with recently reported photoinduced transitions from charge-density and spin-density waves to a metal. Our data demonstrate the nonthermal character of the superconducting-to-normal-state photoinduced phase transition. The data are analyzed using an ad-hoc time-dependent Rothwarf-Taylor model, opening the question of the order of this nonequilibrium phase transition.