Figure 1
Metal–insulator phase diagram (adapted by Imada et al., 1998) based on the Hubbard model. Because the Mott insulating phase occurs at half-filling and when the on-site Coulomb repulsion U is much larger than the hopping energy t and the associated bandwidth, a transition may occur changing the ratio U/t and/or the filling parameter n. In addition to the filling and bandwidth mechanisms, frustration may also play a role in MITs. With a third coordinate the diagram points out three possible MIT routes: the FC-MIT (filling-control MIT) by doping away from half-filling, the BC-MIT (bandwidth-control MIT) by decreasing the ratio U/t and also a frustration-controlled transition (FrC-MIT). |