Temperature and doping dependence of the Bi-Sr-Ca-Cu-O electronic structure and fluctuation effects

Abstract

Angle-resolved photoemission data from bulk ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ show changes in the excitation gap and line shape versus both doping and temperature. We employ two different quantitative analyses; one to search for a gap closing temperature ${T}^{\ensuremath{\star}},$ and the other to further characterize its relation to the superconducting transition temperature ${T}_{c}.$ We present observations of the sharp feature near crystal momentum $\mathbf{k}=(1,0)$ in superconducting spectra, and its temperature and doping dependence. This temperature dependence is analyzed together with the shift in the spectral weight's lowest binding energy (leading edge). Finally, we find evidence for persistence of this sharp peak at temperatures slightly above ${T}_{c}.$