53,753 research outputs found
Exotic Topological States with Raman-Induced Spin-Orbit Coupling
We propose a simple experimental scheme to realize simultaneously the
one-dimensional spin-orbit coupling and the staggered spin-flip in ultracold
pseudospin- atomic Fermi gases trapped in square optical lattices. In the
absence of interspecies interactions, the system supports gapped Chern
insulators and gapless topological semimetal states. By turning on the -wave
interactions, a rich variety of gapped and gapless inhomogeneous topological
superfluids can emerge. In particular, a gapped topological Fulde-Ferrell
superfluid, in which the chiral edge states at opposite boundaries possess the
same chirality, is predicted.Comment: 11 pages, 6 figure
On quasi-local Hamiltonians in General Relativity
We analyse the definition of quasi-local energy in GR based on a Hamiltonian
analysis of the Einstein-Hilbert action initiated by Brown-York. The role of
the constraint equations, in particular the Hamiltonian constraint on the
timelike boundary, neglected in previous studies, is emphasized here. We argue
that a consistent definition of quasi-local energy in GR requires, at a
minimum, a framework based on the (currently unknown) geometric well-posedness
of the initial boundary value problem for the Einstein equations.Comment: 9 page
Single crystal growth and physical properties of SrFe(AsP)
We report a crystal growth and physical properties of
SrFe(AsP). The single crystals for various s were
grown by a self flux method. For , reaches the maximum value of
30\,K and the electrical resistivity () shows -linear dependence.
As increases, decreases and () changes to -behavior,
indicating a standard Fermi liquid. These results suggest that a magnetic
quantum critical point exists around .Comment: 4 pages, 4 figures, accepted to Supplemental issue of the Journal of
Physical Society of Japan (JPSJ
Periodic Variation of Stress in Sputter Deposited Si/WSi2 Multilayers
A tension increment after sputter deposition of 1 nm of WSi2 onto sputtered
Si was observed at low Ar gas pressures. Wafer curvature data on multilayers
were found to have a periodic variation corresponding to the multilayer period,
and this permitted statistical analyses to improve the sensitivity to small
stresses. The observation of tension instead of compression in the initial
stage of growth is new and a model invoking surface rearrangement is invoked.
The data also bear on an unusual surface smoothing phenomena for sputtered Si
surfaces caused by the sputter deposition of WSi2 . We furthermore report that
for low Ar pressures the Si layers are the predominant source of built-up
stress
Optical study of phase transitions in single-crystalline RuP
RuP single crystals of MnP-type orthorhombic structure were synthesized by
the Sn flux method. Temperature-dependent x-ray diffraction measurements reveal
that the compound experiences two structural phase transitions, which are
further confirmed by enormous anomalies shown in temperature-dependent
resistivity and magnetic susceptibility. Particularly, the resistivity drops
monotonically upon temperature cooling below the second transition, indicating
that the material shows metallic behavior, in sharp contrast with the
insulating ground state of polycrystalline samples. Optical conductivity
measurements were also performed in order to unravel the mechanism of these two
transitions. The measurement revealed a sudden reconstruction of band structure
over a broad energy scale and a significant removal of conducting carriers
below the first phase transition, while a charge-density-wave-like energy gap
opens below the second phase transition.Comment: 5 pages, 6 figure
A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars
A comprehensive model atom for Fe with more than 3000 energy levels is
presented. As a test and first application of this model atom, Fe abundances
are determined for the Sun and five stars with well determined stellar
parameters and high-quality observed spectra. Non-LTE leads to systematically
depleted total absorption in the Fe I lines and to positive abundance
corrections in agreement with the previous studies, however, the magnitude of
non-LTE effect is smaller compared to the earlier results. Non-LTE corrections
do not exceed 0.1 dex for the solar metallicity and mildly metal-deficient
stars, and they vary within 0.21 dex and 0.35 dex in the very metal-poor stars
HD 84937 and HD 122563, respectively, depending on the assumed efficiency of
collisions with hydrogen atoms. Based on the analysis of the Fe I/Fe II
ionization equilibrium in these two stars, we recommend to apply the Drawin
formalism in non-LTE studies of Fe with a scaling factor of 0.1. For the Fe II
lines, non-LTE corrections do not exceed 0.01 dex in absolute value. The solar
non-LTE abundance obtained from 54 Fe I lines is 7.56+-0.09 and the abundance
from 18 Fe II lines varies between 7.41+-0.11 and 7.56+-0.05 depending on the
source of the gf-values. Thus, gf-values available for the iron lines are not
accurate enough to pursue high-accuracy absolute abundance determinations.
Lines of Fe I give, on average, a 0.1 dex lower abundance compared to those of
Fe II lines for HD 61421 and HD 102870, even when applying a differential
analysis relative to the Sun. A disparity between Fe I and Fe II points to
problems of stellar atmosphere modelling or/and effective temperature
determination.Comment: 19 pages, 8 figures, online material, accepted by A&
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