Quasiparticle dynamics in high-temperature superconductors far from equilibrium: An indication of pairing amplitude without phase coherence

International audienceWe perform time-resolved photoelectron spectroscopy measurements of optimally doped Bi2Sr2CaCu2O8+δ(Bi-2212) and Bi2Sr2−xLaxCuO6+δ (Bi-2201). The electron dynamics shows that inelastic scattering by nodalquasiparticles decreases when the temperature is lowered below the critical value of the superconductingphase transition. This drop in electronic dissipation is astonishingly robust and survives to photoexcitationdensities much larger than the value sustained by long-range superconductivity. The unconventional behavior ofquasiparticle scattering is ascribed to superconducting correlations extending on a length scale comparable to theinelastic path. Our measurements indicate that strongly driven superconductors enter in a regime without phasecoherence but finite pairing amplitude. The latter vanishes near to the critical temperature and has no evident linkto the pseudogap observed by angle-resolved photoelectron spectroscopy