3,648 research outputs found
Ballistic spin field-effect transistors: Multichannel effects
We study a ballistic spin field-effect transistor (SFET) with special
attention to the issue of multi-channel effects. The conductance modulation of
the SFET as a function of the Rashba spin-orbit coupling strength is
numerically examined for the number of channels ranging from a few to close to
100. Even with the ideal spin injector and collector, the conductance
modulation ratio, defined as the ratio between the maximum and minimum
conductances, decays rapidly and approaches one with the increase of the
channel number. It turns out that the decay is considerably faster when the
Rashba spin-orbit coupling is larger. Effects of the electronic coherence are
also examined in the multi-channel regime and it is found that the coherent
Fabry-Perot-like interference in the multi-channel regime gives rise to a
nested peak structure. For a nonideal spin injector/collector structure, which
consists of a conventional metallic ferromagnet-thin insulator-2DEG
heterostructure, the Rashba-coupling-induced conductance modulation is strongly
affected by large resonance peaks that arise from the electron confinement
effect of the insulators. Finally scattering effects are briefly addressed and
it is found that in the weakly diffusive regime, the positions of the resonance
peaks fluctuate, making the conductance modulation signal sample-dependent.Comment: 18 pages, 15 figure
ANALYSIS OF IMMUNE GENE EXPRESSION IN ROCK BREAM SPLEEN AFTER ROCK BREAM IRIDOVIRUS INFECTION BY TRANSCRIPTOME SEQUENCING
ANALYSIS OF IMMUNE GENE EXPRESSION IN ROCK BREAM SPLEEN AFTER ROCK BREAM IRIDOVIRUS INFECTION BY TRANSCRIPTOME SEQUENCING
Low energy proton-proton scattering in effective field theory
Low energy proton-proton scattering is studied in pionless effective field
theory. Employing the dimensional regularization and MS-bar and power
divergence subtraction schemes for loop calculation, we calculate the
scattering amplitude in 1S0 channel up to next-to-next-to leading order and fix
low-energy constants that appear in the amplitude by effective range
parameters. We study regularization scheme and scale dependence in separation
of Coulomb interaction from the scattering length and effective range for the
S-wave proton-proton scattering.Comment: 23 pages, 6 eps figures, revised considerably, accepted for
publication in Phys. Rev.
Optical properties of iron-based superconductor LiFeAs single crystal
We have measured the reflectivity spectra of the iron based superconductor
LiFeAs (Tc = 17.6 K) in the temperature range from 4 to 300 K. In the
superconducting state (T < Tc), the clear opening of the optical absorption gap
was observed below 25 cm-1, indicating an isotropic full gap formation. In the
normal state (T > Tc), the optical conductivity spectra display a typical
metallic behavior with the Drude type spectra at low frequencies, but we found
that the introduction of the two Drude components best fits the data,
indicating the multiband nature of this superconductor. A theoretical analysis
of the low temperature data (T=4K < Tc) also suggests that two superconducting
gaps best fit the data and their values were estimated as {\Delta}1 = 1.59 meV
and {\Delta}2 = 3.15 meV, respectively. Using the Ferrell-Glover-Tinkham (FGT)
sum rule and dielectric function {\epsilon}1({\omega}), the superconducting
plasma frequency ({\omega}ps) is consistently estimated to be 6,665 cm-1,
implying that about 59 % of the free carriers in the normal state condenses
into the SC condensate. To investigate the various interband transition
processes (for {\omega} > 200 cm-1), we have also performed the local-density
approximation (LDA) band calculation and calculated the optical spectra of the
interband transitions. The theoretical results provided a qualitative agreement
with the experimental data below 4000 cm-1Comment: 19 pages, 5 figures. This paper has been accepted for publication in
New Journal of Physic
Rheological method for alpha test evaluation of developing superplasticizers' performance: Channel flow test
Advance in high-range water-reducing admixture revolutionizes the workability and constructability of conventional vibrated concrete as well as self-consolidating concrete. Its need from construction fields has increased, and consequently a variety of new-type polycarboxylates, base polymers for the admixture, are being formulated in these days. Synthesizing new polymers needs a quick, but reliable, test to evaluate its performance on concrete. The test is also asked for selecting the best applicable brand of them before a test concrete will be mixed. This paper proposes a channel flow test and its usage for the purpose. The proposed procedure for the test includes the mix proportion of a test mortar, the test method, and rheological interpretation of the test results.ope
An Efficient Photoelectrochemical Hydrogen Evolution System using Silicon Nanomaterials with Ultra‐High Aspect Ratios
We fabricated ultra‐high aspect ratio silicon nanomaterials, including a silicon nanomesh and silicon nanowire array, on a wafer scale for efficient photoelectrochemical hydrogen production. These silicon nanomaterials (feature size≈20 nm) possess a high aspect ratio to increase the optical absorptivity of the cells to approximately 95 % over a broad range of wavelengths. The silicon nanomesh and Si nanowire cells achieved high photocurrent values of 13 and 28 mA cm −2 , respectively, which are increased by 200 % and 570 % in comparison to their bulk counterparts. In addition, these scalable Si nanomaterials remained stable for up to 100 min of hydrogen evolution. Detailed studies on the doping and geometrical structures of the resulting hydrogen evolution cells suggest that both the n + pp + doping and thickness of nanostructures are keys to the enhancement of the hydrogen evolution efficiency. The results obtained in this work show that these silicon nanomaterials can be used for high‐performance water‐splitting system applications. The straight doping: Wafer‐scale ultra‐high aspect ratio Si nanomesh/nanowires (feature size≈20 nm) were fabricated and utilized to produce an efficient photoelectrochemical hydrogen evolution system. The Si nanomesh cell yielded extreme optical absorptivity, high external quantum efficiency, and high photocurrent. Detailed studies suggest that both the n + pp + doping and thickness of nanostructures are keys to the enhancement of the hydrogen evolution efficiency.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109595/1/ente_201402074_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109595/2/889_ftp.pd
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