Infrared Spectroscopic Evidences Of Strong Electronic Correlations In (Sr1-Xlax)(3)Ir2o7

We report on infrared spectroscopic studies of the electronic response of the (Sr1-xLax)(3)Ir2O7 system. Our experiments revealed hallmarks of strong electronic correlations in the evolution of the electronic response across the filling-controlled insulator-metal transition. We observed a collapse of the J(eff) = 1/2 Mott gap accompanying the transfer of the spectral weight from the high-energy region to the gap region with electron doping. The intraband conductivity at the metallic side of the transition was found to consist of coherent Drude-like and incoherent responses. The sum rule and the extended Drude model analyses further indicated a large mass enhancement. Our results demonstrate a critical role of the electronic correlations in the charge dynamics of the (Sr1-xLax)(3)Ir2O7 system.