13,745 research outputs found
Optical Control of Topological Quantum Transport in Semiconductors
Intense coherent laser radiation red-detuned from absorption edge can
reactively activate sizable Hall type charge and spin transport in n-doped
paramagnetic semiconductors as a consequence of k-space Berry curvature
transferred from valence band to photon-dressed conduction band. In the
presence of disorder, the optically induced Hall conductance can change sign
with laser intensity.Comment: to appear in Phys. Rev. Let
Possible discovery of the r-process characteristics in the abundances of metal-rich barium stars
We study the abundance distributions of a sample of metal-rich barium stars
provided by Pereira et al. (2011) to investigate the s- and r-process
nucleosynthesis in the metal-rich environment. We compared the theoretical
results predicted by a parametric model with the observed abundances of the
metal-rich barium stars. We found that six barium stars have a significant
r-process characteristic, and we divided the barium stars into two groups: the
r-rich barium stars (, [La/Nd]\,) and normal barium stars. The
behavior of the r-rich barium stars seems more like that of the metal-poor
r-rich and CEMP-r/s stars. We suggest that the most possible formation
mechanism for these stars is the s-process pollution, although their abundance
patterns can be fitted very well when the pre-enrichment hypothesis is
included. The fact that we can not explain them well using the s-process
nucleosynthesis alone may be due to our incomplete knowledge on the production
of Nd, Eu, and other relevant elements by the s-process in metal-rich and super
metal-rich environments (see details in Pereira et al. 2011).Comment: 5 pages, 5 figures, accepted for publication in A&
Berry phase effect in anomalous thermoelectric transport
We develop a theory of Berry phase effect in anomalous transport in
ferromagnets driven by statistical forces such as the gradient of temperature
or chemical potential. Here a charge Hall current arises from the Berry phase
correction to the orbital magnetization rather than from the anomalous velocity
which does not exist in the absence of a mechanical force. A finite-temperature
formula for the orbital magnetization is derived, which enables us to provide
an explicit expression for the off-diagonal thermoelectric conductivity, to
establish the Mott relation between the anomalous Nernst and Hall effects, and
to reaffirm the Onsager relations between reciprocal thermoelectric
conductivities. A first-principles evaluation of our expression is carried out
for the material CuCrSeBr, obtaining quantitative agreement
with a recent experiment.Comment: Published version in PR
Bose and Fermi gases in the early universe with self-gravitational effect
We study the self-gravitational effect on the equation of state (EoS) of Bose
and Fermi gases in thermal equilibrium at the end of reheating, the period
after quark-hadron transition and before Big Bang Nucleosynthesis (BBN). After
introducing new grand canonical partition functions based on the work of
Uhlenbeck and Gropper, we notice some interesting features of the newly
developed EoSs with distinct behaviors of relativistic and non-relativistic
gases under self-gravity. The usual negligence of the self-gravitational effect
when solving the background expansion of the early universe is justified with
numerical results, showing the magnitude of the self-gravitational modification
of the state constant to be less than . This helps us to clarify
the background thermal evolution of the primordial patch. Such clarification is
crucial in testing gravity theories, evaluating inflation models and
determining element abundances in BBN.Comment: 10 pages, 2 figures, to appear in PR
Derivation of the transverse force on a moving vortex in a superfluid
We describe an exact derivation of the total nondissipative transverse force
acting on a quantized vortex moving in a uniform background. The derivation is
valid for neutral boson or fermion superfluids, provided the order parameter is
a complex scalar quantity. The force is determined by the one-particle density
matrix far away from the vortex core, and is found to be the Magnus force
proportional to the superfluid density.Comment: Latex, 6 page
Atomic and electronic structures of neutral and charged boron and boron-rich clusters
Ab initio molecular orbital theory based on both density functional formalism and quantum chemical methods has been used to calculate the equilibrium geometries, binding energies, ionization potentials, fragmentation patterns, and electronic structures of neutral and charged boron clusters containing up to six atoms. Calculations have also been performed on restricted geometries for BnX (n=1,5,12; X=Be, B, C) and B20 clusters to see if clusters can be designed so as to increase their stability. Energetics of doubly chargedB++n clusters have also been studied to find the critical size for Coulomb explosion. The results are compared with existing experimental and theoretical data
Vanishing viscosity limits for the degenerate lake equations with Navier boundary conditions
The paper is concerned with the vanishing viscosity limit of the
two-dimensional degenerate viscous lake equations when the Navier slip
conditions are prescribed on the impermeable boundary of a simply connected
bounded regular domain. When the initial vorticity is in the Lebesgue space
with , we show the degenerate viscous lake equations
possess a unique global solution and the solution converges to a corresponding
weak solution of the inviscid lake equations. In the special case when the
vorticity is in , an explicit convergence rate is obtained
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