Impurity-driven Insulator-to-Metal Transition in VO₂

抄録

In a strongly correlated material VO_2 (3d^1, half filling), undergoing the insulator-to-metal transition (IMT, or metal-to-insulator transition (MIT)) and the structural phase transition near T_c=340 K, the mechanism of the IMT is still controversial due to unclear mechanism inducing the IMT. In particular, the correlated Coulomb interaction between electrons is not understood in experimental data. This is attributed to insufficient theoretical analysis in the Mott transition. In this presentation, impurity effect, observed by temperature dependences of both Hall effect and optical conductivity (new data is here shown), is theoretically analyzed on the basis of pseudopotential and Hubbard model. In conclusion, a result that the impurities break the critical Coulomb interaction is obtained; this is an impurity-induced IMT.