Orbital-selective mass enhancements in multiband Ca2-xSrxRuO4 systems analyzed by the extended Drude model

We investigated optical spectra of quasi-two-dimensional multiband Ca2-xSrxRuO4 systems. The extended Drude model analysis on the ab-plane optical conductivity spectra indicates that the effective mass should be enhanced near x = 0.5. Based on the sum rule argument, we showed that the orbital-selective Mott-gap opening for the d(yz/zx) bands, the widely investigated picture, could not be the origin of the mass enhancement. We exploited the multiband effects in the extended Drude model analysis, and demonstrated that the intriguing heavy mass state near x = 0.5 should come from the renormalization of the d(xy) band.