Ultrafast Raman probe of the photoinduced superconducting to normal state transition in the cuprate Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$
We report an ultrafast Time-Resolved Raman scattering study of the out-of-equilibrium photoinduced dynamics across the superconducting to normal state phase transition of the cuprate Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$. Using the polarization-resolved momentum space selectivity of Raman scattering, we track the superconducting condensate destruction and recovery dynamics with sub-picoseconds time resolution in the anti-nodal region of the Fermi surface where the superconducting gap is maximum. Leveraging ultrafast Raman thermometry, we find a significant dichotomy between the superconducting condensate and the quasiparticle temperature dynamics near the anti-nodes, which cannot be framed in terms of a single effective electron temperature. The present work demonstrates the ability of Time-Resolved Raman scattering to selectively probe out-of-equilibrium pathways of different electronic sub-degrees of freedom during a photoinduced phase transition.