In-plane optical conductivity of La2-xSrxCuO4:: Reduced superconducting condensate and residual Drude-like response -: art. no. 094508

Temperature dependencies of the optical spectra of La2-xSrxCuO4 with x=0.12 and 0.15 were carefully examined for a polarization parallel to the CuO2-plane over a wide frequency range down to 8 cm(-1). Selection of well-characterized crystals enabled us to measure purely in-plane polarized spectra without any additional peak. The weight of superconducting (SC) condensate estimated from the missing area in sigma(1)(omega) well agrees with the estimate from the slope of sigma(2)(omega) vs 1/omega plot, showing no evidence that the Ferrell-Glover-Tinkham sum-rule is violated in the optical spectrum. We demonstrate that the optically estimated SC condensate is much smaller than the value obtained from the mu SR measurement of magnetic penetration depth. We also find an anomalous increase of conductivity in submillimeter region towards omega=0 below T-c, which suggests the microscopic inhomogeneity in the superconducting state. Both observations are discussed in relation with the inhomogeneous electronic state that might be inherent to high-T-c cuprates.