Study of the optical conductivity of Bi2Sr2CaCu2O8+δ material

► The Matsubara-Nambu and the Kubo formula are essential for the optical conductivity. ► In the superconducting state the optical response is characterized by a sharp peak. ► The peak in conductivity is the consequence of standard BCS coherence peak. ► The results compare well with experiment within the Marginal Fermi Liquid ansatz. ► The temperature dependence of the conductivity is consistent with experiment.