44,303 research outputs found
Theoretical spin-wave dispersions in the antiferromagnetic phase AF1 of MnWO based on the polar atomistic model in P2
The spin wave dispersions of the low temperature antiferromagnetic phase
(AF1) MnWO have been numerically calculated based on the recently reported
non-collinear spin configuration with two different canting angles. A
Heisenberg model with competing magnetic exchange couplings and single-ion
anisotropy terms could properly describe the spin wave excitations, including
the newly observed low-lying energy excitation mode =0.45 meV
appearing at the magnetic zone centre. The spin wave dispersion and intensities
are highly sensitive to two differently aligned spin-canting sublattices in the
AF1 model. Thus this study reinsures the otherwise hardly provable hidden polar
character in MnWO.Comment: 7 pages, 5 figure
Probing electronic excitations in molecular conduction
We identify experimental signatures in the current-voltage (I-V)
characteristics of weakly contacted molecules directly arising from excitations
in their many electron spectrum. The current is calculated using a
multielectron master equation in the Fock space of an exact diagonalized model
many-body Hamiltonian for a prototypical molecule. Using this approach, we
explain several nontrivial features in frequently observed I-Vs in terms of a
rich spectrum of excitations that may be hard to describe adequately with
standard one-electron self-consistent field (SCF) theories.Comment: Significantly different content -- inadequacy of SCF approach
described with simple model, and a whole new class of experiments showing
gate modulated current steps discussed in terms of excitations in the
molecular many-body spac
Photon-meson transition form factors of light pseudoscalar mesons
The photon-meson transition form factors of light pseudoscalar mesons , , and are systematically calculated in a
light-cone framework, which is applicable as a light-cone quark model at low
and is also physically in accordance with the light-cone pQCD approach
at large . The calculated results agree with the available experimental
data at high energy scale. We also predict the low behaviors of the
photon-meson transition form factors of , and , which are measurable in process via Primakoff
effect at JLab and DESY.Comment: 22 Latex pages, 7 figures, Version to appear in PR
Towards an improved understanding of eta --> gamma^* gamma^*
We argue that high-quality data on the reaction
will allow one to determine the double off-shell form factor in a model-independent way with controlled accuracy. This is
an important step towards a reliable evaluation of the hadronic light-by-light
scattering contribution to the anomalous magnetic moment of the muon. When
analyzing the existing data for in the range of
total energies , we demonstrate that the
double off-shell form factor is
consistent with the commonly employed factorization ansatz at least for
, if the effect of the meson is taken into account.
However, better data are needed to draw firm conclusions.Comment: 7 pages, 3 figure
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