1,597 research outputs found
A self-consistent first-principles calculation scheme for correlated electron systems
A self-consistent calculation scheme for correlated electron systems is
created based on the density-functional theory (DFT). Our scheme is a
multi-reference DFT (MR-DFT) calculation in which the electron charge density
is reproduced by an auxiliary interacting Fermion system. A short-range
Hubbard-type interaction is introduced by a rigorous manner with a residual
term for the exchange-correlation energy. The Hubbard term is determined
uniquely by referencing the density fluctuation at a selected localized
orbital. This strategy to obtain an extension of the Kohn-Sham scheme provides
a self-consistent electronic structure calculation for the materials design.
Introducing an approximation for the residual exchange-correlation energy
functional, we have the LDA+U energy functional. Practical self-consistent
calculations are exemplified by simulations of Hydrogen systems, i.e. a
molecule and a periodic one-dimensional array, which is a proof of existence of
the interaction strength U as a continuous function of the local fluctuation
and structural parameters of the system.Comment: 23 pages, 8 figures, to appear in J. Phys. Condens. Matte
Spectral function of the spiral spin state in the trestle and ladder Hubbard model
Eder and Ohta have found a violation of the Luttinger rule in the spectral
function for the t-t'-J model, which was interpreted as a possible breakdown of
the Tomonaga-Luttinger(TL) description in models where electrons can pass each
other. Here we have computed the spin correlation along with the spectral
function for the one-dimensional t-t' Hubbard model and two-leg Hubbard ladder.
By varying the Hubbard U we have identified that such a phenomenon is in fact a
spinless-fermion-like behavior of holes moving in a spiral spin configuration
that has a spin correlation length of the system size.Comment: 3 pages, RevTex, 8 figures in Postscript, to be published in Phys.
Rev. B (rapid communication
Spin-twist driven persistent current in a strongly correlated two-dimensional electron system: a manifestation of the gauge field
A persistent current, coupled with the spin state, of purely many-body origin
is shown to exist in Nagaoka's ferromagnetic state in two dimensions (2D). This
we regard as a manifestation of a gauge field, which comes from the surrounding
spin configuration and acts on the hole motion, being coupled to the
Aharonov-Bohm flux. This provides an example where the electron-electron
interaction exerts a profound effect involving the spins in clean
two-dimensional lattice systems in sharp contrast to continuum or spinless
fermion systems.Comment: 11 pages, typeset using Revtex 3.0, Phys. Rev. B in press, 2 figures
available upon request at [email protected]
New Constraints on Radiative Decay of Long-Lived Particles in Big Bang Nucleosynthesis with New He Photodisintegration Data
A recent measurement of He photodisintegration reactions,
He(,)H and He(,)He with laser-Compton
photons shows smaller cross sections than those estimated by other previous
experiments at MeV. We study big-bang nucleosynthesis
with the radiative particle decay using the new photodisintegration cross
sections of He as well as previous data. The sensitivity of the yields of
all light elements D, T, He, He, Li, Li and Be to the cross
sections is investigated. The change of the cross sections has an influence on
the non-thermal yields of D, He and He. On the other hand, the
non-thermal Li production is not sensitive to the change of the cross
sections at this low energy, since the non-thermal secondary synthesis of
Li needs energetic photons of MeV. The non-thermal
nucleosynthesis triggered by the radiative particle decay is one of candidates
of the production mechanism of Li observed in metal-poor halo stars
(MPHSs). In the parameter region of the radiative particle lifetime and the
emitted photon energy which satisfies the Li production above the abundance
level observed in MPHSs, the change of the photodisintegration cross sections
at MeV as measured in the recent experiment leads to
% reduction of resulting He abundance, whereas the Li
abundance does not change for this change of the cross sections of
He(,)H and He(,)He. The Li abundance,
however, could show a sizable change and therefore the future precise
measurement of the cross sections at high energy 50 MeV is
highly required.Comment: 10 pages, 7 figures, conclusion not changed, to be published in PR
Flat-band ferromagnetism induced by off-site repulsions
Density matrix renormalization group method is used to analyze how the
nearest-neighbor repulsion V added to the Hubbard model on 1D triangular
lattice and a railway trestle (t-t') model will affect the electron-correlation
dominated ferromagnetism arising from the interference (frustration). Obtained
phase diagram shows that there is a region in smaller-t' side where the
critical on-site repulsion above which the system becomes ferromagnetic is
reduced when the off-site repulsion is introduced.Comment: 4 pages, RevTex, 6 figures in Postscript, to be published in Phys.
Rev.
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