In-plane optical spectral weight transfer in optimally dopedBi2Sr2Ca2Cu3O10

Abstract

We examine the redistribution of the in-plane optical spectral weight in the normal and superconducting state in trilayer ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{Ca}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{10}$ (Bi2223) near optimal doping $({T}_{c}=110\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ on a single crystal via infrared reflectivity and spectroscopic ellipsometry. We report the temperature dependence of the low-frequency integrated spectral weight $W({\ensuremath{\Omega}}_{c})$ for different values of the cutoff energy ${\ensuremath{\Omega}}_{c}$. Two different model-independent analyses consistently show that for ${\ensuremath{\Omega}}_{c}=1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, which is below the charge transfer gap, $W({\ensuremath{\Omega}}_{c})$ increases below ${T}_{c}$, implying the lowering of the kinetic energy of the holes. This is opposite to the BCS scenario, but it follows the same trend observed in the bilayer compound ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8}$ (Bi2212). The size of this effect is larger in Bi2223 than in Bi2212, approximately scaling with the critical temperature. In the normal state, the temperature dependence of $W({\ensuremath{\Omega}}_{c})$ is close to ${T}^{2}$ up to $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$.