28,231 research outputs found
Kondo correlation and spin-flip scattering in spin-dependent transport through a quantum dot coupled to ferromagnetic leads
We investigate the linear and nonlinear dc transport through an interacting
quantum dot connected to two ferromagnetic electrodes around Kondo regime with
spin-flip scattering in the dot. Using a slave-boson mean field approach for
the Anderson Hamiltonian having finite on-site Coulomb repulsion, we find that
a spin-flip scattering always depresses the Kondo correlation at arbitrary
polarization strength in both parallel and antiparallel alignment of the lead
magnetization and that it effectively reinforces the tunneling related
conductance in the antiparallel configuration. For systems deep in the Kondo
regime, the zero-bias single Kondo peak in the differential conductance is
split into two peaks by the intradot spin-flip scattering; while for systems
somewhat further from the Kondo center, the spin-flip process in the dot may
turn the zero-bias anomaly into a three-peak structure.Comment: 4 pages, 2 figure
Phase equilibrium in two orbital model under magnetic field
The phase equilibrium in manganites under magnetic field is studied using a
two orbital model, based on the equivalent chemical potential principle for the
competitive phases. We focus on the magnetic field induced melting process of
CE phase in half-doped manganites. It is predicted that the homogenous CE phase
begins to decompose into coexisting ferromagnetic phase and CE phase once the
magnetic field exceeds the threshold field. In a more quantitative way, the
volume fractions of the two competitive phases in the phase separation regime
are evaluated.Comment: 4 pages, 4 figure
Generation of high-energy monoenergetic heavy ion beams by radiation pressure acceleration of ultra-intense laser pulses
A novel radiation pressure acceleration (RPA) regime of heavy ion beams from
laser-irradiated ultrathin foils is proposed by self-consistently taking into
account the ionization dynamics. In this regime, the laser intensity is
required to match with the large ionization energy gap when the successive
ionization of high-Z atoms passing the noble gas configurations [such as
removing an electron from the helium-like charge state to
]. While the target ions in the laser wing region are ionized
to low charge states and undergo rapid dispersions due to instabilities, a
self-organized, stable RPA of highly-charged heavy ion beam near the laser axis
is achieved. It is also found that a large supplement of electrons produced
from ionization helps preserving stable acceleration. Two-dimensional
particle-in-cell simulations show that a monoenergetic beam
with peak energy and energy spread of is obtained by
lasers at intensity .Comment: 5 pages, 4 figure
Chiral Properties of Pseudoscalar Mesons on a Quenched Lattice with Overlap Fermions
The chiral properties of the pseudoscalar mesons are studied numerically on a
quenched lattice with the overlap fermion. We elucidate the role of the
zero modes in the meson propagators, particularly that of the pseudoscalar
meson. The non-perturbative renormalization constant is determined from
the axial Ward identity and is found to be almost independent of the quark mass
for the range of quark masses we study; this implies that the error is
small. The pion decay constant, , is calculated from which we
determine the lattice spacing to be 0.148 fm. We look for quenched chiral log
in the pseudoscalar decay constants and the pseudoscalar masses and we find
clear evidence for its presence. The chiral log parameter is
determined to be in the range 0.15 -- 0.4 which is consistent with that
predicted from quenched chiral perturbation theory.Comment: Version accepted for publication by PRD. A few minor typographical
errors have been corrected. 24 pages, 11 figure
Quantum criticality and nodal superconductivity in the FeAs-based superconductor KFe2As2
The in-plane resistivity and thermal conductivity of
FeAs-based superconductor KFeAs single crystal were measured down to 50
mK. We observe non-Fermi-liquid behavior at =
5 T, and the development of a Fermi liquid state with when
further increasing field. This suggests a field-induced quantum critical point,
occurring at the superconducting upper critical field . In zero field
there is a large residual linear term , and the field dependence of
mimics that in d-wave cuprate superconductors. This indicates that
the superconducting gaps in KFeAs have nodes, likely d-wave symmetry.
Such a nodal superconductivity is attributed to the antiferromagnetic spin
fluctuations near the quantum critical point.Comment: 4 pages, 4 figures - replaces arXiv:0909.485
Pion Decay Constant, and Chiral Log from Overlap Fermions
We report our calculation of the pion decay constant , the axial
renormalization constant , and the quenched chiral logarithms from the
overlap fermions. The calculation is done on a quenched lattice at
fm using tree level tadpole improved gauge action. The smallest pion
mass we reach is about 280 MeV. The lattice size is about 4 times the Compton
wavelength of the lowest mass pion.Comment: Lattice2001(Hadronic Matrix Elements), 3pages, 5figure
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