Spin singlet and quasiparticle excitations in cuprate superconductors

We followed step by the transition from an antiferromagnetic (AFM) Mott insulator to a superconducting (SC) metal in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ (Bi-2212) cuprate using electronic Raman scattering spectroscopy. This was achieved tracking doping dependence of spin singlet excitation (SSE) originating AFM insulator, normal-state quasiparticle related mobile charge carriers, and Bogoliubov quasiparticles SC gap. show that signature pseudogap phase which develops during this can be interpreted as blocking carriers enhancement correlations temperature drops. find energy scale pseudogap, ${\mathrm{\ensuremath{\Delta}}}_{\text{pg}}(p)$, closely follows SSE, ${\mathrm{\ensuremath{\Delta}}}_{\text{sse}}(p)$ with $p$. The lifetime considerably increases when collapses. reveal maximum amplitude gap ${\mathrm{\ensuremath{\Delta}}}_{\text{sc}}^{\text{max}}$ ${T}_{\mathrm{c}}$ are linked extended range doping, such ${\mathrm{\ensuremath{\Delta}}}_{\text{sc}}^{\text{max}}(p)\ensuremath{\propto}{\mathrm{\ensuremath{\Delta}}}_{\text{sse}}(p)\phantom{\rule{0.16em}{0ex}}{T}_{\mathrm{c}}\phantom{\rule{0.16em}{0ex}}(p)$. relation suggests play key role mechanism superconductivity.