Study on the decisive factor for metal-insulator transitions in a LaVO 3 Mott-Hubbard insulator.

The decisive physical parameters on electrical conduction in a LaVO 3 Mott-Hubbard system are systematically investigated by analyzing pure, Ca-, and Sr-doped samples. The Rietveld refinement of the X-ray diffraction data indicates that a drastic change occurs along the c -axis to reduce the octahedral tilt thereby relaxing the distortion for the doped compounds, in contrast to an insignificant change in the in-plane distortion. From electrical, optical, and photoemission measurements, both Ca and Sr-doping in LaVO 3 induce insulator to metal transitions under a similar hole carrier concentration as suppressing the Mott-gap excitation. Fitting results on temperature-dependent resistivity based on various conduction models indicate that the most localized conduction behavior takes place for the highly distorted pure LaVO 3 , while disordered Fermi liquid behavior starts to appear for moderately distorted Ca-doped LaVO 3 . The least distorted Sr-doped LaVO 3 exhibits fully delocalized conduction governed by a non-Fermi-liquid-like behavior in the whole temperature range. Our analysis indicates that the difference in the transport mechanism arises from the differing degree of hybridization of the V 3d and O 2p states in the pure and doped systems, strongly associated with the structural distortion.