Metal-insulator transition in pure and Cr-dopedV2O3

Abstract

On the basis of our theoretical examination of the insulating state of ${\mathrm{V}}_2$ ${\mathrm{O}}_3$ reported in the preceding two papers and the experimental results of NMR and susceptibility measurements of the metallic phase, we conjecture the highly correlated electron-gas character in this latter phase of ${\mathrm{V}}_2$ ${\mathrm{O}}_3$. We present arguments for the first-order metal-insulator transition which we consider to be entropy driven passing from the insulating state to a paramagnetic metallic one of nearly equal inner energy but considerably different entropy due to the breakdown of the magnetic and orbital long-range order present in the insulating phase. We believe that the origin of the highly correlated electron gas in the paramagnetic metallic phase lies in the stability of the electronic molecular state of the V pairs along the $c$ axis which persist through the metallic phase, a picture which estimates extremely well the observed entropy in this phase. The lattice distortion observed in the insulating phase is believed to be purely magnetostrictive and of no direct importance to the transition mechanism.