Metal–Insulator Transition in κ-(ET)2X and (DCNQI)2M: Two Contrasting Manifestation of Electron Correlation

One of the clear manifestations of electron correlation in condensed matter is metal–insulator (MI) transition. The organic conductors κ-(ET) 2 X and (DCNQI) 2 M are contrasting textbook materials exhibiting correlation-induced MI transition in a single-π band with half filling and a π– d hybrid multiband with tunable band filling, respectively. By comparing these two systems, we learn prototypical manifestations of electron correlation in purely electronic and lattice-coupled manners.