Electron Localization and Structural Distortions in the Metal-Insulator Transition of Simple Oxides

摘要

We report on electron-phonon interactions as a main common property in simple oxides deduced from infrared measurements, and search, using X-ray absorption techniques, a local structure counterpart associated to it. We found that temperature dependent electron localization is determinant in explaining the conductivity in RNiQ_3 (R= rare earth) and in La_(0.67)Ca_(0.33) MnO_3 and their metal-insulator phase transitions. This is also associated to a tower symmetry lattice distortion in the insulating phase. The mechanism established from comparison of the experimental conductivity obtained from reflectivity spectra with that from Reik's theory suggests small polaron hopping as the principle lor electron displacement in an oxygen high polarizable lattice. We also comment our preliminary results on the temperature dependent consequence of Jahn-Teller and GdFeO_3 lattice distortions in the insulator YVO_3.