Numerical Study for the Ground State of Multi-Orbital Hubbard Models

Abstract

Ground state properties of multi-orbital Hubbard models are investigated by the auxiliary field quantum Monte Carlo method. A Monte Carlo technique generalized to the multi-orbital systems is introduced and examined in detail. The algorithm contains non-trivial cases where the negative sign problem does not exist. We investigate one-dimensional systems with doubly degenerate orbitals by this new technique. Properties of the Mott insulating state are quantitatively clarified as the strongly correlated insulator, where the charge gap amplitude is much larger than the spin gap. The insulator-metal transitions driven by the chemical potential shows a universality class with the correlation length exponent $\nu =1/2$, which is consistent with the scaling arguments. Increasing level split between two orbitals drives crossover from the Mott insulator with high spin state to the band insulator with low spin state, where the spin gap amplitude increases and becomes closer to the charge gap. Experimental relevance of our results especially to Haldane materials is discussed.

36 pages LaTeX including 17 PS figures, to be published in J.Phys.Soc.Jpn. 67 (1998) vol.9

References in corpus (4)

• A Quantum Monte Carlo Method and Its Applications to Multi-Orbital Hubbard Models
• Slave-Boson Mean-Field Theory of the Antiferromagnetic State in the Doubly Degenerate Hubbard Model - the Half-Filled Case -
• Generalization of Gutzwiller Approximation
• The Metal-Insulator Transition in the Doubly Degenerate Hubbard Model

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• Orbital-selective Mott-Hubbard transition in the two-band Hubbard model
• Stability of a metallic state in the two-orbital Hubbard model
• A new numerical algorithm for the double-orbital Hubbard model -- Hund-coupled pairing symmetry in the doped case
• Heavy Quasi-Particle in the Two-Orbital Hubbard Model
• Auxiliary Field Quantum Monte Carlo for Multiband Hubbard Models: Controlling the Sign and Phase Problems to Capture Hund's Physics
• A novel continuous time quantum Monte Carlo solver for dynamical mean field theory in the compact Legendre representation
• Sign-Free Determinant Quantum Monte Carlo Study of Excitonic Density Orders in a Two-Orbital Hubbard-Kanamori Model