  For inhomogeneous high-T_c superconductors, hole-driven metal-insulator
transition (MIT) theory explains that the gradual increase of conductivity with
increasing hole doping is due to inhomogeneity with the local Mott system
undergoing the first-order MIT and the local non-Mott system. For VO_2, a
monoclinic and correlated metal (MCM) phase showing the linear characteristic
as evidence of the Mott MIT is newly observed by applying electric field and
temperature. The structural phase transition occurs between MCM and Rutile
metal phases. Devices using the MIT are named MoBRiK.

Strongly Correlated Electrons;Superconductivity