Metal-insulator transition in the two-orbital hubbard model at fractional band fillings: Self-energy functional approach

R. Bulla, Thomas Pruschke, Alex C. Hewson

Kensuke Inaba, Akihisa Koga

We investigate the infinite-dimensional two-orbital Hubbard model at arbitrary band fillings. By means of the self-energy functional approach, we discuss the stability of the metallic state in the systems with same and different bandwidths. It is found that the Mott insulating phases are realized at commensurate band fillings. Furthermore, it is clarified that the orbital selective Mott phase with one orbital localized and the other itinerant is stabilized even at fractional band fillings in the system with different bandwidths.

R. Eder, C. Gröber, M. G. Zacher +1 more

Hisashi Kondo, Tôru Moriya

Antiferromagnetic and metal to insulator transitions in the ground state of two-dimensional half-filled and nearly half-filled Hubbard models with the nearest neighbor and the second nearest neighbor transfers (- t and t ′ , respectively) are studied by using the Green's function approach with the self-energy up to the second order in the coupling constant U . For a choice of the parameter value t ′ / t =0.2 the half-filled model undergoes the first order phase transition between paramagnetic metallic (PM) phase and antiferromagnetic insulator (AFI) phase at U / t =4.0 while the first order transition between PM and antiferromagnetic metallic (AFM) phases takes place for nearly half-filled band. The one-electron spectral density is calculated for the PM, AFM, and AFI phases near the phase boundaries. In the PM phase the quasi-particle dispersion indicates the band narrowing from the Hartree-Fock results and the flat band behavior as was indicated by previous stadies and was observed in high- T c cuprates. The quasi-particle dispersion in the AFM phase is seen to be close to the Hartree-Fock results.

E. G. Goryachev, Evgeniy V. Kuz’min, Sergei G. Ovchinnikov

Tomoko Kita, Takuma Ohashi, Norio Kawakami

We investigate the Mott transitions in the three-orbital Hubbard model by means of the dynamical mean field theory with continuous-time quantum Monte Carlo simulations. We obtain the phase diagram determined in the orbital level splitting versus Hubbard interaction plane in the case of two electrons per site. It is also found that the introduction of holes into the orbital selective Mott insulating phase induces the metallic state with heavy quasiparticles.