Scaling properties of the optical conductivity of Bi-based cuprates

We present novel infrared optical conductivity data on the three layer high Tc superconductor Bi2Sr2Ca2Cu3O10 at optimal doping. We extend the analysis of an earlier publication, providing a universal scaling function σ (ω, T) = T−1g (ω/T) for the optical conductivity. In the present manuscript, we obtain a good scaling collapse of the experimental curves on the g (ω/T) over a wide range of values of ω/T (at least in range 0–10), if we assume that g (ω/T) is superimposed on a non-universal background which is temperature independent. We obtain the same result, if in our analysis we allow this background to have a T2 temperature dependent correction. The most striking property of g (ω/T) is, that it corresponds to a scattering rate which varies linearly as a function of temperature, but which is independent of the frequency.