High-temperature optical behavior of Bi-based cuprates

The optical conductivity σ(ω) and the optical spectral weight W provide important information about the physical properties of strongly correlated systems. This is the case for cuprates, where DMFT calculations have shown the important role of the quasiparticle renormalization factor Z, which manifests itself in a strong temperature (T) dependence of W at low T. We analyze here new experimental results for the normal phase of two Bi-based cuprates up to 500 K. The comparison between our DMFT calculations and the experimental data for W allows for a full understanding of the observed deviation (∝T4) from the low-temperature T2 behavior in the framework of a Sommerfeld expansion with strongly renormalized coefficients.