Strong lattice correlation of non-equilibrium quasiparticles in a pseudospin-1/2 Mott insulator Sr₂IrO₄

In correlated oxides the coupling of quasiparticles to other degrees of freedom such as spin and lattice plays critical roles in the emergence of symmetry-breaking quantum ordered states such as high temperature superconductivity. We report a strong lattice coupling of photon-induced quasiparticles in spin-orbital coupling Mott insulator Sr 2 IrO 4 probed via optical excitation. Combining time-resolved X-ray diffraction and optical spectroscopy techniques, we reconstruct a spatiotemporal map of the diffusion of these quasiparticles. Due to the unique electronic configuration of the quasiparticles, the strong lattice correlation is unexpected but extends the similarity between Sr 2 IrO 4 and cuprates to a new dimension of electron-phonon coupling which persists under highly non-equilibrium conditions.