390 research outputs found
Stripe Charge Ordering in Triangular-Lattice Systems
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 phases, but we observe in common
that one or two orbitals among three orbitals become relevant due to the effect
of orbital arrangement. It is found that charge stripes stabilized by the
nearest-neighbor Coulomb interaction consist of antiferromagnetic/ferro-orbital
chains for small Hund's coupling, while there occurs stripe charge ordering
with ferromagnetic/antiferro-orbital chains for large Hund's coupling.Comment: 2 pages, 2 figures, Proceedings of LT24 (August 10-17, 2005, Orlando
Spin-charge-orbital ordering on triangle-based lattices
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 degenerate, the zigzag
chain is decoupled to a doble-chain spin system to suppress the spin
frustration due to the spatial anisotropy of the occupied orbital. On the other
hand, when the level splitting is increased and the orbital anisotropy
disappears, a characteristic change in the spin incommnsurability is observed
due to the revival of the spin frustration.Comment: 2 pages, 1 figure, Proceedings of SCES'05 (July 26-30, 2005, Vienna
Spin-Orbit Interaction Effects in the Electronic Structure of B20-type CoSi: First-Principles Density Functional Study
We have performed fully relativistic first-principles density functional
calculations for non-magnetic B20-type CoSi. The spin-orbit interaction has
crucial effects on the electronic structures of a chiral crystal. The
calculated band structure around the Fermi energy shows Bloch vector -linear
dispersion expressed by a - Weyl Hamiltonian, i.e., a mass-less
Dirac Hamiltonian. We found the hedgehog-like spin texture in Bloch
-vector space (momentum space) on the isoenergy surface around
the point. The Fermi velocity for -linear dispersion is about
0.22, where is the Fermi velocity of graphene.Comment: 6 pages, SCES 2013, accepted for publication in JPS Conf. Pro
Key Role of Orbital Anisotropy in Geometrically Frustrated Electron System
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, zigzag chain and ladder. In
the zigzag chain, the system is effectively regarded as a decoupled double
chain of the S=1/2 antiferromagnetic Heisenberg model, and the spin gap is
approximately zero, similar to the case of weakly coupled Heisenberg chains. On
the other hand, in the ladder, the spin correlation on the rung remains robust
and the spin gap exists.Comment: 2 pages, 2 figures, Proceedings of SCES'04 (July 26-30, 2004,
Karlsruhe
Spin-orbital gap of multiorbital antiferromagnet
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 method. Due to the appearance
of a ferro-orbital arrangement, the system is regarded as a one-orbital system,
while the degree of spin frustration is controlled by the spatial anisotropy of
the orbital. In the region of strong spin frustration, we observe a finite
energy gap between ground and first-excited states, which should be called a
spin-orbital gap. The physical meaning is clarified by an effective Heisenberg
spin model including correctly the effect of the orbital arrangement influenced
by the spin excitation.Comment: 8 pages, 6 figures, extended versio
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