Temperature-modulation analysis of superconductivity-induced transfer of in-plane spectral weight inBi2Sr2CaCu2O8

Abstract

We examine the superconductivity-induced redistribution of optical spectral weight in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8}$ near optimal doping using a detailed Kramers-Kronig consistency analysis of the kink (slope change) at ${T}_{c}$ of the temperature-dependent optical spectra, published earlier [H. J. A. Molegraaf et al., Science 295, 2239 (2002)]. We demonstrate that the temperature dependence of the complex dielectric function at high frequencies (above $0.75\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$) imposes the most stringent limits on the possible changes of the low-frequency integrated spectral weight. The presented calculations provide additional arguments, supporting the previous conclusion about a superconductivity-induced increase of the integrated low-frequency spectral weight below ${T}_{c}$. The Ferrell-Glover-Tinkham sum rule is not satisfied well above $2.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, which indicates that this increase is caused by the transfer of spectral weight from the interband to the intraband region and only partially by the narrowing of the Drude peak.