49 research outputs found
Rare Decays of \Lambda_b->\Lambda + \gamma and \Lambda_b ->\Lambda + l^{+} l^{-} in the Light-cone Sum Rules
Within the Standard Model, we investigate the weak decays of and with the light-cone
sum rules approach. The higher twist distribution amplitudes of
baryon to the leading conformal spin are included in the sum rules for
transition form factors. Our results indicate that the higher twist
distribution amplitudes almost have no influences on the transition form
factors retaining the heavy quark spin symmetry, while such corrections can
result in significant impacts on the form factors breaking the heavy quark spin
symmetry. Two phenomenological models (COZ and FZOZ) for the wave function of
baryon are also employed in the sum rules for a comparison, which can
give rise to the form factors approximately 5 times larger than that in terms
of conformal expansion. Utilizing the form factors calculated in LCSR, we then
perform a careful study on the decay rate, polarization asymmetry and
forward-backward asymmetry, with respect to the decays of , .Comment: 38 pages, 15 figures, some typos are corrected and more references
are adde
Critical thickness for ferroelectricity and magnetoelectric effect in multiferroic tunnel junction with symmetrical and asymmetrical electrodes
The critical thickness for ferroelectricity and magnetoelectric effects have been
investigated for the multiferroic tunnel junction with symmetric and asymmetric metallic
electrodes based on density functional theory. The ferroelectric polarization of a barrier
is still retained down to 2 unit cells scale for the asymmetric multiferroic tunnel
junction. The greater cause, leading to the reduction, or even complete elimination for
the critical thickness, is the difference in the work function for the two asymmetrical
electrodes. In addition, the effect of magnetoelectric coupling is obvious. The asymmetric
multiferroic tunnel junction provides the possibility for the miniaturising and
multifunctional spin electronic devices
First-principle study of the electronic structures and ferroelectric properties in BaZnF 4
The electronic structures and ferroelectric properties of barium fluoride
BaZnF4 were investigated by employing ab initio calculations based on the
density-functional theory within generalized gradient approximation. We
discussed the possible origin of ferroelectricity of BaZnF4 by the
analysis of Born effective charges, orbital-resolved density of states, and
distribution of charge density. The results show that the barium and
fluorine atoms are very important polarization unity. The calculated
spontaneous polarization of 14.2 μC/cm2 by using Berry-phase approach
is reasonable agreement with previous experimental data. Barium fluorides
are promising candidates for use in nonvolatile memories devices