5,123 research outputs found
Atomically straight steps on vicinal Si (111) surfaces prepared by step-parallel current in the kink-up direction
We demonstrate that annealing of a vicinal Si(111) surface at about 800 C
with a direct current in the direction that ascends the kinks enhances the
formation of atomically straight step edges over micrometer lengths, while
annealing with a current in the opposite direction does not. Every straight
step edge has the same atomic configuration U(2,0), which is useful as a
template for the formation of a variety of nanostructures. A phenomenological
model based on electromigration of charged mobile atoms explains the observed
current-polarity dependent behavior.Comment: Accepted for publication in Appl. Phys. Lett. Numbers of pages and
figures are 12 and 4, respectivel
Solitons in Chern-Simons theories of nonrelativistic CP^{N-1} models: Spin textures in the quantum Hall effect
Topological solitons in CP^{N-1} models coupled with Chern-Simons gauge
theory and a Hopf term are studied both analytically and numerically.These
models are low-energy effective theories for the quantum Hall effect with
internal degrees of freedom, like that in bilayer electron systems. We
explicitly show that the CP^{N-1} models describe quite well spin textures in
the original Chern-Simons theory of bosonized electrons.Comment: Latex, 19 pages, 6 figure
Performance of Trial Embankment on Soft Clay
This paper is concerned with the interpretation of the observed and predicted performances of a full-scale trial embankment, which was constructed for the design purposes regarding a new bypass road to be constructed over soft clay adjacent to existing structures. The prediction based on the finite element analyses and the determination of soil parameters are briefly outlined. The results of comparison show adequate agreement between the predicted and observed field time-dependent deformation behavior throughout the entire loading history. However, if the predictions from the present FE-analyses are made by using the soil parameters measured in the laboratory, a correction factor of 6 on the value of coefficient of consolidation is required to obtain reasonable agreement with the field behavior. Finally, the practical suggestions are made for assessing the effect on the nearby existing structures of soil movements towards the outside of embankment
Extending spin dephasing time of perfectly aligned Nitrogen-Vacancy centers by mitigating stress distribution on highly misoriented chemical-vapor-deposition diamond
Extending the spin-dephasing time (T2*) of perfectly aligned nitrogen-vacancy
(NV) centers in large-volume chemical vapor deposition (CVD) diamonds leads to
enhanced DC magnetic sensitivity. However, T2* of the NV centers is
significantly reduced by the stress distribution in the diamond film as its
thickness increases. To overcome this issue, we developed a method to mitigate
the stress distribution in the CVD diamond films, leading to a T2* extension of
the ensemble NV centers. CVD diamond films of approximately 50 \mu m thickness
with perfectly aligned NV centers were formed on (111) diamond substrates with
misorientation angles of 2.0, 3.7, 5.0, and 10{\deg}. We found that T2* of the
ensemble of NV centers increased to approach the value limited only by the
electron and nuclear spin bath with increasing the misorientation angle.
Microscopic stress measurements revealed that the stress distribution was
highly inhomogeneous along the depth direction in the CVD diamond film at low
misorientation angles, whereas the inhomogeneity was largely suppressed on
highly misoriented substrates. The reduced stress distribution possibly
originates from the reduction of the dislocation density in the CVD diamond.
This study provides an important method for synthesizing high-quality diamond
materials for use in highly sensitive quantum sensors
Affleck-Dine leptogenesis via multiscalar evolution in a supersymmetric seesaw model
A leptogenesis scenario in a supersymmetric standard model extended with
introducing right-handed neutrinos is reconsidered. Lepton asymmetry is
produced in the condensate of a right-handed sneutrino via the Affleck-Dine
mechanism. The LH_u direction develops large value due to a negative effective
mass induced by the right-handed sneutrino condensate through the Yukawa
coupling of the right-handed neutrino, even if the minimum during the inflation
is fixed at the origin. The lepton asymmetry is nonperturbatively transfered to
the LH_u direction by this Yukawa coupling.Comment: 19 pages, 3 figures. Revised version for publication. The model was
modified to fix some problem
Cosmological constraints on dark matter models with velocity-dependent annihilation cross section
We derive cosmological constraints on the annihilation cross section of dark
matter with velocity-dependent structure, motivated by annihilating dark matter
models through Sommerfeld or Breit-Wigner enhancement mechanisms. In models
with annihilation cross section increasing with decreasing dark matter
velocity, big-bang nucleosynthesis and cosmic microwave background give
stringent constraints.Comment: 23 pages, 9 figures; Added reference
A Theoretical Light-Curve Model for the Recurrent Nova V394 Coronae Austrinae
A theoretical light curve for the 1987 outburst of V394 Coronae Austrinae
(V394 CrA) is modeled to obtain various physical parameters of this recurrent
nova. We then apply the same set of parametersto a quiescent phase and confirm
that these parameters give a unified picture of the binary. The early visual
light curve (1-10 days after the optical maximum) is well reproduced by a
thermonuclear runaway model on a very massive WD close to the Chandrasekhar
limit (1.37 +- 0.01 M_sun). The ensuing plateau phase (10-30 days) is also
reproduced by the combination of a slightly irradiated MS and a fully
irradiated flaring-up disk with a radius ~1.4 times the Roche lobe size. The
best fit parameters are the WD mass 1.37 M_sun, the companion mass 1.5 M_sun
(0.8-2.0 M_sun is acceptable), the inclination angle of the orbit i~65-68
degree, and the flaring-up rim ~0.30 times the disk radius. The envelope mass
at the optical peak is estimated to be ~6 x 10^{-6} M_sun, which indicates an
average mass accretion rate of 1.5 x 10^{-7} M_sun yr^{-1} during the quiescent
phase between the 1949 and 1987 outbursts. In the quiescent phase, the observed
light curve can be reproduced with a disk size of 0.7 times the Roche lobe size
and a rather slim thickness of 0.05 times the accretion disk size at the rim.
About 0.5 mag sinusoidal variation of the light curve requires the mass
accretion rate higher than ~1.0 x 10^{-7} M_sun yr^{-1}, which is consistent
with the above estimation from the 1987 outburst. These newly obtained
quantities are exactly the same as those predicted in a new progenitor model of
Type Ia supernovae.Comment: 9 pages including 4 figures, to appear in the Astrophysical Journal,
Part
Measurement of Single and Double Spin-Flip Probabilities in Inelastic Deuteron Scattering on 12C at 270 MeV
The deuteron single and double spin-flip probabilities, S1 and S2, have been
measured for the 12C(pol{d},pol{d}') reaction at Ed = 270 MeV for an excitation
energy range between 4 and 24 MeV and a scattering angular range between
Theta_lab = 2.5 and 7.5 deg. The extracted S1 exhibits characteristic values
depending on the structure of the excited state. The S2 is close to zero over
the measured excitation energy range. The SFP angular distribution data for the
2+ (4.44 MeV) and 1+ (12.71 MeV) states are well described by the microscopic
DWIA calculations
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