33,452 research outputs found
A new effective interaction for the trapped Fermi gas
We apply the configuration-interaction method to calculate the spectra of
two-component Fermi systems in a harmonic trap, studying the convergence of the
method at the unitary interaction limit. We find that for a fixed
regularization of the two-body interaction the convergence is exponential or
better in the truncation parameter of the many-body space. However, the
conventional regularization is found to have poor convergence in the
regularization parameter, with an error that scales as a low negative power of
this parameter. We propose a new regularization of the two-body interaction
that produces exponential convergence for systems of three and four particles.
From the systematics, we estimate the ground-state energy of the
four-particle system to be (5.05 +- 0.024)hbar omega.Comment: 4 pages, 3 figure
Topology of the polarization field in ferroelectric nanowires from first principles
The behaviour of the cross-sectional polarization field is explored for thin
nanowires of barium titanate from first-principles calculations. Topological
defects of different winding numbers have been obtained, beyond the known
textures in ferroelectric nanostructures. They result from the inward
accommodation of the polarization patterns imposed at the surface of the wire
by surface and edge effects. Close to a topological defect the polarization
field orients out of the basal plane in some cases, maintaining a close to
constant magnitude, whereas it virtually vanishes in other cases.Comment: 4 pages, 3 figure
LDA+Gutzwiller Method for Correlated Electron Systems
Combining the density functional theory (DFT) and the Gutzwiller variational
approach, a LDA+Gutzwiller method is developed to treat the correlated electron
systems from {\it ab-initio}. All variational parameters are self-consistently
determined from total energy minimization. The method is computationally
cheaper, yet the quasi-particle spectrum is well described through kinetic
energy renormalization. It can be applied equally to the systems from weakly
correlated metals to strongly correlated insulators. The calculated results for
SrVO, Fe, Ni and NiO, show dramatic improvement over LDA and LDA+U.Comment: 4 pages, 3 figures, 1 tabl
Pinning control of fractional-order weighted complex networks
In this paper, we consider the pinning control problem of fractional-order weighted complex dynamical networks. The well-studied integer-order complex networks are the special cases of the fractional-order ones. The network model considered can represent both directed and undirected weighted networks. First, based on the eigenvalue analysis and fractional-order stability theory, some local stability properties of such pinned fractional-order networks are derived and the valid stability regions are estimated. A surprising finding is that the fractional-order complex networks can stabilize itself by reducing the fractional-order q without pinning any node. Second, numerical algorithms for fractional-order complex networks are introduced in detail. Finally, numerical simulations in scale-free complex networks are provided to show that the smaller fractional-order q, the larger control gain matrix D, the larger tunable weight parameter , the larger overall coupling strength c, the more capacity that the pinning scheme may possess to enhance the control performance of fractional-order complex networks
Lateral shift of the transmitted light beam through a left-handed slab
It is reported that when a light beam travels through a slab of left-handed
medium in the air, the lateral shift of the transmitted beam can be negative as
well as positive. The necessary condition for the lateral shift to be positive
is given. The validity of the stationary-phase approach is demonstrated by
numerical simulations for a Gaussian-shaped beam. A restriction to the slab's
thickness is provided that is necessary for the beam to retain its profile in
the traveling. It is shown that the lateral shift of the reflected beam is
equal to that of the transmitted beam in the symmetric configuration.Comment: 14 pages, 4 figure
Two successive field-induced spin-flop transitions in single-crystalline CaCoAs
CaCoAs, a ThCrSi-structure compound, undergoes an
antiferromagnetic transition at \emph{T}=76K with the magnetic moments
being aligned parallel to the \emph{c} axis. Electronic transport measurement
reveals that the coupling between conducting carriers and magnetic order in
CaCoAs is much weaker comparing to the parent compounds of iron
pnictide. Applying magnetic field along \emph{c} axis induces two successive
spin-flop transitions in its magnetic state. The magnetization saturation
behaviors with \emph{\textbf{H}c} and \emph{\textbf{H}ab}
at 10K indicate that the antiferromagnetic coupling along \emph{c} direction is
very weak. The interlayer antiferromagntic coupling constant \emph{J} is
estimated to be about 2 meV.Comment: Accepted for publication in Phys. Rev. B. 5 pages, 6 figure
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