1,898 research outputs found
Manipulation of spin dephasing in InAs quantum wires
The spin dephasing due to the Rashba spin-orbit coupling, especially its
dependence on the direction of the electric field is studied in InAs quantum
wire. We find that the spin dephasing is strongly affected by the angle of
Rashba effective magnetic field and the applied magnetic field. The
nonlinearity in spin dephasing time versus the direction of the electric field
shows a potential evenue to manipulate the spin lifetime in spintronic device.
Moreover, we figure out a quantity that can well represent the inhomogeneous
broadening of the system which may help us to understand the many-body spin
dephasing due to the Rashba effect.Comment: 4 pages, 3 figure
Kinetics of spin coherence of electrons in an undoped semiconductor quantum well
We study the kinetics of spin coherence of optically excited electrons in an
undoped insulating ZnSe/ZnCdSe quantum well under moderate magnetic
fields in the Voigt configuration. After clarifying the optical coherence and
the spin coherence, we build the kinetic Bloch equations and calculate
dephasing and relaxation kinetics of laser pulse excited plasma due to
statically screened Coulomb scattering and electron hole spin exchange. We find
that the Coulomb scattering can not cause the spin dephasing, and that the
electron-hole spin exchange is the main mechanism of the spin decoherence.
Moreover the beat frequency in the Faraday rotation angle is determined mainly
by the Zeeman splitting, red shifted by the Coulomb scattering and the electron
hole spin exchange. Our numerical results are in agreement with experiment
findings. A possible scenario for the contribution of electron-hole spin
exchange to the spin dephasing of the -doped material is also proposed.Comment: 12 pages, RevTex, 11 figures, scheduled to publish in PRB Jan. 15,
200
Onsager Relations and Hydrodynamic Balance Equations in 2D Quantum Wells
In this letter we clarify the role of heat flux in the hydrodynamic balance
equations in 2D quantum wells, facilitating the formulation of an Onsager
relation within the framework of this theory. We find that the Onsager relation
is satisfied within the framework of the 2D hydrodynamic balance equation
transport theory at sufficiently high density. The condition of high density is
consonant with the requirement of strong electron-electron interactions for the
validity of our balance equation formulation.Comment: 11 pages, RevTex, 4 postscript figures are avaliable upon reques
Theory of photoinduced charge transfer in weakly coupled donor-acceptor conjugated polymers: application to an MEH-PPV:CN-PPV pair
In a pair of coupled donor-acceptor conjugated polymer chains, it is possible
for an exciton photoexcited on either polymer to decay into a hole in the donor
polymer's valence band and an electron in the conduction band of the acceptor
polymer. We calculate the corresponding exciton decay rate and its dependence
on inter-polymer distance. For a pair of derivatives of poly(phenylene
vinylene), PPV, specifically poly[2-methoxy, 5-(2-ethyl-hexyloxy)-1, 4
PPV], MEH-PPV, and poly(2,5-hexyloxy -phenylene cyanovinylene), CN-PPV, at a
separation of 6 \AA the characteristic decay time is 2.2 ps, whereas at 4 \AA
it is fs.Comment: 9 pages, RevTeX, 4 PS files, to be published in a special issue of
Chem. Phy
Spin-dependent hole quantum transport in Aharonov-Bohm ring structure: possible schemes for spin filter
We study the Aharonov-Bohm (AB) effect in two-dimensional mesoscopic frame in
hole systems. We show that differing from the AB effect in electron systems,
due to the presence of both the heavy hole and the light hole, the conductances
not only show the normal spin-unresolved AB oscillations, but also become
spin-separated. Some schemes for spin filter based on the abundant interference
characteristics are proposed.Comment: 4 pages, 5 figures. Phys. Lett. A, 2005, in pres
A virtual intersubband spin-flip spin-orbit coupling induced spin relaxation in GaAs (110) quantum wells
A spin relaxation mechanism is proposed based on a second-order spin-flip
intersubband spin-orbit coupling together with the spin-conserving scattering.
The corresponding spin relaxation time is calculated via the Fermi golden rule.
It is shown that this mechanism is important in symmetric GaAs (110) quantum
wells with high impurity density. The dependences of the spin relaxation time
on electron density, temperature and well width are studied with the underlying
physics analyzed.Comment: 4+ pages, 4 figures, to be published in Solid Stat. Commu
Hawking Radiation of Dirac Particles in an Arbitrarily Accelerating Kinnersley Black Hole
Quantum thermal effect of Dirac particles in an arbitrarily accelerating
Kinnersley black hole is investigated by using the method of generalized
tortoise coordinate transformation. Both the location and the temperature of
the event horizon depend on the advanced time and the angles. The Hawking
thermal radiation spectrum of Dirac particles contains a new term which
represents the interaction between particles with spin and black holes with
acceleration. This spin-acceleration coupling effect is absent from the thermal
radiation spectrum of scalar particles.Comment: Revtex, 12pt, 16 pages, no figure, to appear in Gen. Rel. Grav. 34
(2002) N0.
Spin relaxation time, spin dephasing time and ensemble spin dephasing time in -type GaAs quantum wells
We investigate the spin relaxation and spin dephasing of -type GaAs
quantum wells. We obtain the spin relaxation time , the spin dephasing
time and the ensemble spin dephasing time by solving the
full microscopic kinetic spin Bloch equations, and we show that, analogous to
the common sense in an isotropic system for conduction electrons, ,
and are identical due to the short correlation time. The
inhomogeneous broadening induced by the D'yakonov-Perel term is suppressed by
the scattering, especially the Coulomb scattering, in this system.Comment: 4 pages, 2 figures, to be published in Phys. Lett.
Pairing in spin polarized two-species fermionic mixtures with mass asymmetry
We discuss on the pairing mechanism of fermions with mismatch in their fermi
momenta due to a mass asymmetry. Using a variational ansatz for the ground
state we also discuss the BCS -BEC crossover of this system. It is shown that
the breached pairing solution with a single fermi surface is stable in the BEC
regime. We also include the temperatures effect on the fermion pairing within
an approximation that is valid for temperatures much below the critical
temperature.Comment: 8 pages and 6 figures, few typos corrected, version to appear in EPJ
Effect of substituting guinea grass with soybean hulls on production performance and digestion traits in fattening rabbits
[EN] The objective of this study was to evaluate the use of soybean hulls (SH) to substitute guinea grass (GG), traditionally used as fibre source in the diets of fattening rabbits on performance, coefficients of total tract apparent digestibility (CTTAD) of nutrients, gastrointestinal tract development and caecum fermentation. A total of 160 mixed sex Hyla commercial meat rabbits were allocated to 4 experimental groups (40 per treatment) differing in the SH level inclusion in the diet offered to rabbits from 40 to 90 d of age: 0, 50, 100 and 200 g/kg as-fed basis: SH0, SH50, SH100 and SH200 groups, respectively. Growth performance was recorded from 40 to 90 d of age, CTTAD of nutrients from 86 to 90 d of age, and gastrointestinal tract development, caecum fermentation and carcass traits were determined at 90 d of age. Average daily feed intake and the feed/gain ratio were lower in SH100 and SH200 groups than in SH0 group (P0.05). In conclusion, our results suggest that SH can substitute GG in the diets of fattening rabbits up to 200 g/kg in diet with no adverse effects on the growth performance, feed efficiency, carcass traits and meat quality.This study was supported by the earmarked fund for Modern Agro-industry Technology Research System (CARS-44-B-1).Shang, S.; Wu, Z.; Liu, G.; Sun, C.; Ma, M.; Li, FC. (2017). Effect of substituting guinea grass with soybean hulls on production performance and digestion traits in fattening rabbits. World Rabbit Science. 25(3):241-249. https://doi.org/10.4995/wrs.2017.6654SWORD24124925
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