Charge dynamics near the electron-correlation induced metal-insulator transition in pyrochlore-type molybdates -: art. no. 266401

The systematics of the bandwidth controlled metal-insulator transition (MIT) are investigated for R2Mo2O7 (R=Nd, Sm, Gd, Dy, and Ho) by measurements of dc and optical conductivity. The substantial role of electron correlation in driving the MIT is verified. With changing the R ionic radius (r) or equivalently the one-electron bandwidth, the T=0 K MIT occurs at r(c)approximate tor(R=Gd). The T=0 K gap continuously vanishes as Deltaproportional to(r(c)-r), while at the metallic side the decrease of Drude weight is followed towards r(c). A high-temperature incoherent state is approached through crossover regions both from the metallic and the insulating state.