385 research outputs found
Insulating Phases Induced by Crossing of Partially Filled Landau Levels in a Si Quantum Well
We study magnetotransport in a high mobility Si two-dimensional electron
system by in situ tilting of the sample relative to the magnetic field. A
pronounced dip in the longitudinal resistivity is observed during the Landau
level crossing process for noninteger filling factors. Together with a Hall
resistivity change which exhibits the particle-hole symmetry, this indicates
that electrons or holes in the relevant Landau levels become localized at the
coincidence where the pseudospin-unpolarized state is expected to be stable.Comment: 4 pages, 4 figure
Well-width dependence of valley splitting in Si/SiGe quantum wells
The valley splitting in Si two-dimensional electron systems is studied using
Si/SiGe single quantum wells (QWs) with different well widths. The energy gaps
for 4 and 5.3 nm QWs, obtained from the temperature dependence of the
longitudinal resistivity at the Landau level filling factor , are much
larger than those for 10 and 20 nm QWs. This is consistent with the well-width
dependence of the bare valley splitting estimated from the comparison with the
Zeeman splitting in the Shubnikov-de Haas oscillations.Comment: 3 pages, 2 figure
Room-Temperature Electron Spin Transport in a Highly Doped Si Channel
We report on the first demonstration of generating a spin current and spin
transport in a highly doped Si channel at room temperature (RT) using a
four-terminal lateral device with a spin injector and a detector consisting of
an Fe/MgO tunnel barrier. Spin current was generated using a nonlocal
technique, and spin injection signals and Hanle-type spin precession were
successfully detected at 300 K, thus proving spin injection with the
elimination of spurious signals. The spin diffusion length and its lifetime at
RT were estimated to be 0.6 \"im and 1.3 ns by the Hanle-type spin precession,
respectively.Comment: 14 pages, 4 Figure
Metallic Behavior of Cyclotron Relaxation Time in Two-Dimensional Systems
Cyclotron resonance of two-dimensional electrons is studied at low
temperatures down to 0.4 K for a high-mobility Si/SiGe quantum well which
exhibits a metallic temperature dependence of dc resistivity . The
relaxation time shows a negative temperature dependence, which
is similar to that of the transport scattering time obtained from
. The ratio at 0.4 K increases as the electron
density decreases, and exceeds unity when approaches the critical
density for the metal-insulator transition.Comment: 4 pages, 3 figure
Spin Drift in Highly Doped n-type Si
A quantitative estimation of spin drift velocity in highly doped n-type
silicon (Si) at 8 K is presented in this letter. A local two-terminal Hanle
measurement enables the detection of a modulation of spin signals from the Si
as a function of an external electric field, and this modulation is analyzed by
using a spin drift-diffusion equation and an analytical solution of the
Hanle-type spin precession. The analyses reveal that the spin drift velocity is
linearly proportional to the electric field. The contribution of the spin drift
effect to the spin signals is crosschecked by introducing a modified nonlocal
four-terminal method.Comment: 16 pages, 3 figure
Remarks on the relativistic Hartree equations
We study the global well-posedness (GWP) and small data scattering of radial solutions of the relativistic Hartree type equations with nonlocal nonlinearity F(u) = ¸(j ¢ j¡° ¤ juj2)u, ¸ 2 R n f0g, 0 < ° < n, n ¸ 3. We establish a weighted L2 Strichartz estimate applicable to non-radial functions and some fractional integral estimates for radial functions
Clustering Properties of Low-Luminosity Star-Forming galaxies at z = 0.24 and 0.40 in the Subaru Deep Field
We present our analysis on the clustering properties of star-forming galaxies
selected by narrow-band excesses in the Subaru Deep Field. Specifically we
focus on Halpha emitting galaxies at z = 0.24 and z = 0.40 in the same field,
to investigate possible evolutionary signatures of clustering properties of
star-forming galaxies. Based on the analysis on 228 Halpha emitting galaxies
with 39.8 < log L(Halpha) < 40.8 at z = 0.40, we find that their two-point
correlation function is estimated as xi = (r/1.62^{+0.64}_{-0.50} Mpc)^{-1.84
+/- 0.08}. This is similar to that of Halpha emitting galaxies in the same
Halpha luminosity range at z = 0.24, xi = (r/1.88^{+0.60}_{-0.49} Mpc)^{-1.89
+/- 0.07}. These correlation lengths are smaller than those for the brighter
galaxy sample studied by Meneux et al. (2006) in the same redshift range. The
evolution of correlation length between z = 0.24 and z = 0.40 is interpreted by
the gravitational growth of the dark matter halos.Comment: 16 pages, 7 figures, PASJ, Vol.60, No.6, in pres
An Intermediate-band imaging survey for high-redshift Lyman Alpha Emitters: The Mahoroba-11
We present results of our intermediate-band optical imaging survey for
high- Ly emitters (LAEs) using the prime focus camera, Suprime-Cam,
on the 8.2m Subaru Telescope. In our survey, we use eleven filters; four
broad-band filters (, , , and ) and seven
intermediate-band filters covering from 500 nm to 720 nm; we call this imaging
program as the Mahoroba-11. The seven intermediate-band filters are selected
from the IA filter series that is the Suprime-Cam intermediate-band filter
system whose spectral resolution is . Our survey has been made in a
sky area in the Subaru XMM Newton Deep Survey
field. We have found 409 IA-excess objects that provide us a large photometric
sample of strong emission-line objects. Applying the photometric redshift
method to this sample, we obtained a new sample of 198 LAE candidates at . We found that there is no evidence for evolution of the number density
and the star formation rate density for LAEs with between and 5.Comment: 46 pages, 15 figures, PASJ, Vol.57, No.6, in pres
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