Ultrafast transient reflectivity measurements of optimally doped Bi2+xSr2−xCaCu2O8+δ with disorder

The effect of disorder in high-${T}_{\mathrm{c}}$ superconductors is investigated from the viewpoint photoinduced quasiparticle (QP) dynamics, obtained through time-resolved pump-probe spectroscopy. We perform measurements on an optimally doped (OPD) ${\mathrm{Bi}}_{2+x}{\mathrm{Sr}}_{2\ensuremath{-}x}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ (Bi2212) with out-of-plane induced by Bi-Sr substitution $(x)$, which present standard Bi2212 but not usually controlled. Based systematic change controlled $x$, we identify changes dynamics QP relaxation and gap formation superconducting (SC) pseudogap (PG) states. onset temperature ${T}^{*}$ PG response increases increase more significant than slight decrease ${T}_{\mathrm{c}}$. These properties are equivalently reflected destruction fluences SC also accelerates times for QPs, can be due to increased phonon scattering probability caused disorder. In contrast, recovery observed strongly excited condition shows identical fluence dependence various implying that does significantly contribute coherent formation.