Photoinduced quasiparticle dynamics of single CuO2 -layer Bi-based cuprates with out-of-plane disorder

Optimally-doped (OPD) ${\mathrm{Bi}}₂{\mathrm{Sr}}_1.7{R}_0.3{\mathrm{CuO}}_{6+\ensuremath{\delta}}$ ($R$-Bi2201, $R=\mathrm{Eu}$ and La) are investigated from the viewpoint of photoinduced nonequilibrium quasiparticle dynamics of high-${T}_{\mathrm{c}}$ cuprates with low ${T}_{\mathrm{c}}$. The temperature dependencies of the superconducting (SC) and pseudogap (PG) responses demonstrate that the out-of-plane disorder enhanced by replacing La with Eu reduces the SC transition temperature and increases the PG energy. SC fluctuations are observed in each sample, especially in $R=\mathrm{La}$, where large SC fluctuations, which deeply penetrate into the PG state, are observed. From the fluence-dependent dynamics, the planar optical destruction energy densities of the SC state are found consistent with the ${T}_{\mathrm{c}}²$ dependence noted previously for other high-${T}_{\mathrm{c}}$ superconductors. Upon an optical quench we find that the SC state recovery starts only after the completion of the PG recovery in both samples.