Nature of the Doping-Driven Metal-Insulator Transition in Correlated Electron Systems with strong Hund's Exchange Coupling

Abstract: We study the doping-driven Mott metal-insulator transition for multi-orbital Hubbard models with Hund's exchange coupling at finite temperatures. As in the single-orbital Hubbard model, the transition is of first-order within dynamical mean field theory, with a coexistence region where two solutions can be stabilized. We find, that in the presence of finite Hund's coupling, the insulating phase is connected to a badly metallic phase, which extends to surprisingly large dopings. While fractional power-law behavior of the self-energies on the Matsubara axis is found on both sides of the transition, a regime with frozen local moments develops only on the branch connected to the insulating phase.