Destabilization of ferromagnetism by frustration and realization of a nonmagnetic Mott transition in the quarter-filled two-orbital Hubbard model

2軌道ハバードモデルのフィリングにおけるフラストレーションによる強磁性の不安定化と非磁性モット転移の実現

久保 勝規 

Kubo, Katsunori

The two-orbital Hubbard model on a square lattice at quarter filling (electron number per site = 1) is investigated by the variational Monte Carlo method. For the variational wave function, we include short-range doublon-holon binding factors. We find that the energy of this wave function is lower than that of the density-density Jastrow wave function partially including long-range correlations used in a previous study. We introduce frustration to the model by the next-nearest-neighbor hopping in addition to the nearest-neighbor hopping . For , a ferromagnetic state with staggered orbital order occurs by increasing the Coulomb interaction before the Mott transition takes place. By increasing , the region of this ferromagnetic phase shrinks, and the Mott transition without magnetic order occurs.