Abstract
The two widely accepted mechanisms of the insulator-metal Mott–Hubbard transitions which have been considered up until now are driven by the band-filling or bandwidth effects. We found a different mechanism of the Mott–Hubbard insulator-metal transition, which is controlled instead by the changes in the Mott–Hubbard energy . In contrast to the changes in the bandwidth in the “bandwidth control” scenario or to the variations of the band-filling parameter in the “band-filling” scenario, a dramatic decrease in the Mott–Hubbard energy plays the key role in this mechanism. We have experimentally observed this type of the insulator metal transition in the transition metal oxide . The decrease in the Mott–Hubbard energy is caused by the high-spin–low-spin crossover in the electronic shell of transition metal ion with configuration under high pressure. The pressure-induced spin crossover in was investigated and confirmed by synchrotron x-ray diffraction, nuclear forward scattering, and x-ray emission methods. The insulator-metal transition at the same pressures was found by the optical absorption and dc resistivity measurements.
- Received 5 July 2007
DOI:https://doi.org/10.1103/PhysRevB.77.155112
©2008 American Physical Society