Antiferro-quadrupole state of orbital-degenerate Kondo lattice model with f^2 configuration (2007)
Onishi, Hiroaki, Hotta, Takashi
To clarify a key role of $f$ orbitals in the emergence of antiferro-quadrupole structure in PrPb$_{3}$, we investigate the ground-state property of an orbital-degenerate Kondo lattice model by...
Deformation of SU(4) singlet spin-orbital state due to Hund's rule coupling (2007)
We investigate the ground-state property and the excitation gap of a one-dimensional spin-orbital model with isotropic spin and anisotropic orbital exchange interactions, which represents the...
Effect of Hund's rule coupling on SU(4) spin-orbital system (2006)
Onishi, Hiroaki, Hotta, Takashi
We investigate the ground-state property of a one-dimensional two-orbital Hubbard model at quarter filling by numerical techniques such as the density-matrix renormalization group method and the...
Spin-orbital gap of multiorbital antiferromagnet (2006)
Onishi, Hiroaki, Hotta, Takashi
In order to discuss the spin-gap formation in a multiorbital system, we analyze an e_g-orbital Hubbard model on a geometrically frustrated zigzag chain by using a density-matrix renormalization group...
Multipole correlations in low-dimensional f-electron systems (2005)
Onishi, Hiroaki, Hotta, Takashi
By using a density matrix renormalization group method, we investigate the ground-state properties of a one-dimensional three-orbital Hubbard model on the basis of a j-j coupling scheme. For $B_4^0...
Stripe Charge Ordering in Triangular-Lattice Systems (2005)
Onishi, Hiroaki, Hotta, Takashi
We investigate the ground-state properties of a t2g-orbital Hubbard model on a triangular lattice at electron density 5.5 by using numerical techniques. There appear several types of paramagnetic...
Spin, charge, and orbital correlations in the one-dimensional t2g-orbital Hubbard model (2005)
Xavier, Jose, Onishi, Hiroaki, Hotta, Takashi, Dagotto, Elbio
We present the zero-temperature phase diagram of the one-dimensional t2g-orbital Hubbard model, obtained using the density-matrix renormalization group and Lanczos techniques. Emphasis is given to...
Spin-charge-orbital ordering on triangle-based lattices (2005)
Onishi, Hiroaki, Hotta, Takashi
We investigate the ground-state property of an e_g-orbital Hubbard model at quarter filling on a zigzag chain by exploiting the density matrix renormalization group method. When two orbitals are...
Orbital-based Scenario for Magnetic Structure of Neptunium Compounds (2004)
Onishi, Hiroaki, Hotta, Takashi
In order to understand a crucial role of orbital degree of freedom in the magnetic structure of recently synthesized neptunium compounds NpTGa_5 (T=Fe, Co, and Ni), we propose to discuss the magnetic...
Suppression of Spin Frustration due to Orbital Selection (2004)
Onishi, Hiroaki, Hotta, Takashi
In order to clarify a crucial role of orbital degree of freedom in geometrically frustrated systems, we investigate both ground- and excited-state properties of the e_g-orbital degenerate Hubbard...
Onishi, Hiroaki, Hotta, Takashi
In order to clarify a key role of orbital degree of freedom in the spin S=1 Haldane system, we investigate ground-state properties of the t2g-orbital degenerate Hubbard model on the linear chain by...
Key Role of Orbital Anisotropy in Geometrically Frustrated Electron System (2004)
Onishi, Hiroaki, Hotta, Takashi
By using the density matrix renormalization group method, we investigate ground- and excited-state properties of the e_g-orbital degenerate Hubbard model at quarter filling for two kinds of lattices,...
Quantum Narrowing Effect in a Spin-Peierls System with Quantum Lattice Fluctuation (2002)
Onishi, Hiroaki, Miyashita, Seiji
We investigate a one-dimensional S=1/2 antiferromagnetic Heisenberg model coupled to quantum lattice vibration using a quantum Monte Carlo method. We study the ground-state lattice fluctuation where...
Spin-Peierls transition of the first order in S=1 antiferromagnetic Heisenberg chains (2000)
Onishi, Hiroaki, Miyashita, Seiji
We investigate a one-dimensional S=1 antiferromagnetic Heisenberg model coupled to a lattice distortion by a quantum Monte Carlo method. Investigating the ground state energy of the static...
Temperature Dependence of Spin and Bond Ordering in a Spin-Peierls System (1999)
Onishi, Hiroaki, Miyashita, Seiji
We investigate thermodynamic properties of a one-dimensional S=1/2 antiferromagnetic Heisenberg model coupled to a lattice distortion by a quantum Monte Carlo method. In particular we study how spin...
Local magnetic structure due to inhomogeneity of interaction in S=1/2 antiferromagnetic chain (1999)
Nishino, Masamichi, Onishi, Hiroaki, Roos, Pascal, Yamaguchi, Kizashi, Miyashita, Seiji
We study the magnetic properties of $S=1/2$ antiferromagnetic Heisenberg chains with inhomogeneity of interaction. Using a quantum Monte Carlo method and an exact diagonalization method, we study...
Quantum Monte Carlo Study on Magnetization Processes (1999)
Onishi, Hiroaki, Nishino, Masamichi, Kawashima, Naoki, Miyashita, Seiji
A quantum Monte Carlo method combining update of the loop algorithm with the global flip of the world line is proposed as an efficient method to study the magnetization process in an external field,...