The charge dynamics of the bandwidth controlled metal-insulation transition (MIT) in pyrochlore R2Mo2O7 (R = Nd, Sm, Dy, and Ho) single crystals was investigated using the measurements of dc and optical conductivity. The importance of 4d electron correlation in driving the MIT phenomena was also investigated. It was observed that with changing the ionic radius (r) of R or equivalently the one-electron bandwidth, the T = 0 K MIT occurred at rc ≈ r, where rc is the critical value of the rare-earth ionic radius. It was also observed that the change in the electronic state and scattering in sample single crystals was due to the zero-temperature quantum MIT.
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