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+δ single crystals (Tc = 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 Tc 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. [ABSTRACT FROM AUTHOR]