1,435 research outputs found
Single Impurity Anderson Model with Coulomb Repulsion between Conduction Electrons on the Nearest-Neighbour Ligand Orbital
We study how the Kondo effect is affected by the Coulomb interaction between
conduction electrons on the basis of a simplified model. The single impurity
Anderson model is extended to include the Coulomb interaction on the
nearest-neighbour ligand orbital. The excitation spectra are calculated using
the numerical renormalization group method. The effective bandwidth on the
ligand orbital, , is defined to classify the state. This quantity
decreases as the Coulomb interaction increases. In the
region, the low energy properties are described by the Kondo state, where
is the hybridization width. As decreases in this region, the
Kondo temperature is enhanced, and its magnitude becomes comparable to
for . In the region, the local
singlet state between the electrons on the and ligand orbitals is formed.Comment: 5 pages, 3 figures, LaTeX, to be published in J. Phys. Soc. Jpn Vol.
67 No.
Large renal aneurysm successfully treated by percutaneous embolization using detachable steel coils
The definitive version is available at www.blackwell-synergy.com.ArticleInternational Journal of Urology. 13(7): 993-994 (2006)journal articl
Affleck-Dine leptogenesis via multiscalar evolution in a supersymmetric seesaw model
A leptogenesis scenario in a supersymmetric standard model extended with
introducing right-handed neutrinos is reconsidered. Lepton asymmetry is
produced in the condensate of a right-handed sneutrino via the Affleck-Dine
mechanism. The LH_u direction develops large value due to a negative effective
mass induced by the right-handed sneutrino condensate through the Yukawa
coupling of the right-handed neutrino, even if the minimum during the inflation
is fixed at the origin. The lepton asymmetry is nonperturbatively transfered to
the LH_u direction by this Yukawa coupling.Comment: 19 pages, 3 figures. Revised version for publication. The model was
modified to fix some problem
Linear Algebraic Calculation of Green's function for Large-Scale Electronic Structure Theory
A linear algebraic method named the shifted
conjugate-orthogonal-conjugate-gradient method is introduced for large-scale
electronic structure calculation. The method gives an iterative solver
algorithm of the Green's function and the density matrix without calculating
eigenstates.The problem is reduced to independent linear equations at many
energy points and the calculation is actually carried out only for a single
energy point. The method is robust against the round-off error and the
calculation can reach the machine accuracy. With the observation of residual
vectors, the accuracy can be controlled, microscopically, independently for
each element of the Green's function, and dynamically, at each step in
dynamical simulations. The method is applied to both semiconductor and metal.Comment: 10 pages, 9 figures. To appear in Phys. Rev. B. A PDF file with
better graphics is available at http://fujimac.t.u-tokyo.ac.jp/lses
NaV2O4: a Quasi-1D Metallic Antiferromagnet with Half-Metallic Chains
NaV2O4 crystals were grown under high pressure using a NaCl flux, and the
crystals were characterized with X-ray diffraction, electrical resistivity,
heat capacity, and magnetization. The structure of NaV2O4 consists of double
chains of edge-sharing VO6 octahedra. The resistivity is highly anisotropic,
with the resistivity perpendicular to the chains more than 20 times greater
than that parallel to the chains. Magnetically, the intrachain interactions are
ferromagnetic and the interchain interactions are antiferromagnetic; 3D
antiferromagnetic order is established at 140 K. First principles electronic
structure calculations indicate that the chains are half metallic.
Interestingly, the case of NaV2O4 seems to be a quasi-1D analogue of what was
found for half-metallic materials.Comment: 14 pages, including 4 figures and 1 table, accepted for publication
in PR
Dynamical simulation of spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin glasses
Spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin
glasses are studied with and without randaom magnetic anisotropy by dynamical
Monte Carlo simulations. In isotropic case, clear evidence of a
finite-temperature chiral-glass transition is presented. While the spin
autocorrelation exhibits only an interrupted aging, the chirality
autocorrelation persists to exhibit a pronounced aging effect reminisecnt of
the one observed in the mean-field model. In anisotropic case, asymptotic
mixing of the spin and the chirality is observed in the off-equilibrium
dynamics.Comment: 4 pages including 5 figures, LaTex, to appear in Phys. Rev. Let
Long-range interactions in the effective low energy Hamiltonian of Sr2IrO4: a core level resonant inelastic x-ray scattering study
We have investigated the electronic structure of Sr2IrO4 using core level
resonant inelastic x-ray scattering. The experimental spectra can be well
reproduced using ab initio density functional theory based multiplet ligand
field theory calculations, thereby validating these calculations. We found that
the low-energy, effective Ir t2g orbitals are practically degenerate in energy.
We uncovered that covalency in Sr2IrO4, and generally in iridates, is very
large with substantial oxygen ligand hole character in the Ir t2g Wannier
orbitals. This has far reaching consequences, as not only the onsite
crystal-field energies are determined by the long range crystal-structure, but,
more significantly, magnetic exchange interactions will have long range
distance dependent anisotropies in the spin direction. These findings set
constraints and show pathways for the design of d^5 materials that can host
compass-like magnetic interactions
Band Calculation for Ce-compounds on the basis of Dynamical Mean Field Theory
The band calculation scheme for electron compounds is developed on the
basis of the dynamical mean field theory (DMFT) and the LMTO method. The
auxiliary impurity problem is solved by a method named as NCAv', which
includes the correct exchange process of the virtual
excitation as the vertex correction to the non-crossing approximation (NCA) for
the fluctuation. This method leads to the correct magnitude
of the Kondo temperature, , and makes it possible to carry out
quantitative DMFT calculation including the crystalline field (CF) and the
spin-orbit (SO) splitting of the self-energy. The magnetic excitation spectra
are also calculated to estimate . It is applied to Ce metal and CeSb
at T=300 K as the first step. In Ce metal, the hybridization intensity (HI)
just below the Fermi energy is reduced in the DMFT band. The photo-emission
spectra (PES) have a conspicuous SO side peak, similar to that of experiments.
is estimated to be about 70 K in -Ce, while to be about
1700 K in -Ce. In CeSb, the double-peak-like structure of PES is
reproduced. In addition, which is not so low is obtained because HI
is enhanced just at the Fermi energy in the DMFT band.Comment: 30pages, 18 figure
Field-Shift Aging Protocol on the 3D Ising Spin-Glass Model: Dynamical Crossover between the Spin-Glass and Paramagnetic States
Spin-glass (SG) states of the 3-dimensional Ising Edwards-Anderson model
under a static magnetic field are examined by means of the standard Monte
Carlo simulation on the field-shift aging protocol at temperature . For each
process with (T; \tw, h), \tw being the waiting time before the field is
switched on, we extract the dynamical crossover time, \tcr(T; \tw, h). We
have found a nice scaling relation between the two characteristic length scales
which are properly determined from \tcr and \tw and then are normalized by
the static field crossover length introduced in the SG droplet theory. This
scaling behavior implies the instability of the SG phase in the equilibrium
limit even under an infinitesimal . In comparison with this numerical result
the field effect on real spin glasses is also discussed.Comment: 4 pages, 5 figures, jpsj2, Changed conten
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