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

Entropy of the Schwarzschild-de Sitter Black Hole due to arbitrary spin fields in different Coordinates

By using the Newman-Penrose formalism and the improved thin-layer ``brick wall'' approach, the statistical-mechanical entropies of the Schwarzschild-de Sitter black hole arising from quantum massless arbitrary spin fields are studied in the Painlev\'e and Lemaitre coordinates. Although the metrics in both the Painlev\'e and the Lemaitre coordinates do not obviously possess the singularities as that in the Schwarzschild-like coordinate, we find that, for arbitrary spin fields, the entropies in the Painlev\'e and Lemaitre coordinates are exactly equivalent to that in the Schwarzschild-like coordinate.Comment: 14 pages, no figure, to be published in JHE

Adsorption of hydrogen molecules on the platinum-doped boron nitride nanotubes

Adsorption of hydrogen molecules on platinum-doped single-walled zigzag (8,0) boron nitride (BN) nanotube is investigated using the density-functional theory. The Pt atom tends to occupy the axial bridge site of the BN tube with the highest binding energy of −0.91 eV. Upon Pt doping, several occupied and unoccupied impurity states are induced, which reduces the band gap of the pristine BN nanotube. Upon hydrogen adsorption on Pt-doped BN nanotube, the first hydrogen molecule can be chemically adsorbed on the Pt-doped BN nanotube without crossing any energy barrier, whereas the second hydrogen molecule has to overcome a small energy barrier of 0.019 eV. At least up to two hydrogen molecules can be chemically adsorbed on a single Pt atom supported by the BN nanotube, with the average adsorption energy of −0.365 eV. Upon hydrogen adsorption on a Pt-dimer-doped BN nanotube, the formation of the Pt dimer not only weakens the interaction between the Pt cluster and the BN nanotube but also reduces the average adsorption energy of hydrogen molecules. These calculation results can be useful in the assessment of metal-doped BN nanotubes as potential hydrogen storage media

Adsorption of hydrogen molecules on the platinum-doped boron nitride nanotubes

Adsorption of hydrogen molecules on platinum-doped single-walled zigzag (8,0) boron nitride (BN) nanotube is investigated using the density-functional theory. The Pt atom tends to occupy the axial bridge site of the BN tube with the highest binding energy of −0.91 eV. Upon Pt doping, several occupied and unoccupied impurity states are induced, which reduces the band gap of the pristine BN nanotube. Upon hydrogen adsorption on Pt-doped BN nanotube, the first hydrogen molecule can be chemically adsorbed on the Pt-doped BN nanotube without crossing any energy barrier, whereas the second hydrogen molecule has to overcome a small energy barrier of 0.019 eV. At least up to two hydrogen molecules can be chemically adsorbed on a single Pt atom supported by the BN nanotube, with the average adsorption energy of −0.365 eV. Upon hydrogen adsorption on a Pt-dimer-doped BN nanotube, the formation of the Pt dimer not only weakens the interaction between the Pt cluster and the BN nanotube but also reduces the average adsorption energy of hydrogen molecules. These calculation results can be useful in the assessment of metal-doped BN nanotubes as potential hydrogen storage media

An atlas of endohedral Sc2S cluster fullerenes

Structural identification is a difficult task in the study of metallofullerenes, but understanding of the mechanism of formation of these structures is a pre-requisite for new high-yield synthetic methods. Here, systematic density functional theory calculations demonstrate that metal sulfide fullerenes Sc2S@Cn have similar cage geometries from C70 to C84 and form a close-knit family of structures related by Endo-Kroto insertion/extrusion of C2 units and Stone-Wales isomerization transformations. The stabilities predicted for favoured isomers by DFT calculations are in good agreement with available experimental observations, have implications for the formation of metallofullerenes, and will aid structural identification from within the combinatorially vast pool of conceivable isomers

Analysis on Effect Decomposition of Industrial COD Emission

AbstractIn this paper, which is based on the effect decomposition model of the emission of pollutants, the change of the industrial COD emission is researched, and a quantitative analysis is carried out for the scale effect, structure effect and technology effect of the industrial COD emission change. The driving factors and causes for this kind of change are identified and the contribution of the three kinds of effects on the pollution reduction is analyzed. The results show that the gradually increasing scale effect is a major factor causing increasing stress on the pollution reduction. The structure effect which is overall low indicates that the activities of optimization and adjustment for the industrial structure have no significant effect. The increment of the generalized technology effect is a main reason for the reduction of the pollution emission. Wherein, the upgrading of industrial technology and the development of scale economy make a great contribution to reduction of pollution. It is an important way to realize the target of pollution reduction by using clean technology effect to offset the new emission and reducing the stock with pollution control effect

Unusual Dissolution Behavior of Tooth Enamel and Synthetic HAP Crystals Under High Partial Saturation Conditions

The dissolution behavior of enamel and synthetic hydroxyapatite in acidic media possessing a high degree of partial saturation was found to be neither simple surface dissolution nor linear with time. Instead, a repetitive, stepwise dissolution pattern was observed. To explain this phenomenon, a model based upon a hypothesis that the crystals dissolve in a synchronized fashion was proposed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66946/2/10.1177_00220345770560051201.pd

Complex-valued Burgers and KdV-Burgers equations

Spatially periodic complex-valued solutions of the Burgers and KdV-Burgers equations are studied in this paper. It is shown that for any sufficiently large time T, there exists an explicit initial data such that its corresponding solution of the Burgers equation blows up at T. In addition, the global convergence and regularity of series solutions is established for initial data satisfying mild conditions

Spin relaxation time, spin dephasing time and ensemble spin dephasing time in nn-type GaAs quantum wells

We investigate the spin relaxation and spin dephasing of $n$-type GaAs quantum wells. We obtain the spin relaxation time $T_1$, the spin dephasing time $T_2$ and the ensemble spin dephasing time $T_2^{\ast}$ 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, $T_1$, $T_2$ and $T_2^{\ast}$ 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.

Sources of CP Violation in the Two-Higgs Doublet Model

Assuming CP violation arises solely through the Higgs potential, we develop the most general two-Higgs doublet model. There is no discrete symmetry that distinguishes the two Higgs bosons. It is assumed that an approximate global family symmetry sufficiently suppresses flavor-changing neutral scalar interactions. In addition to a CKM phase, neutral boson mixing, and superweak effects, there can be significant CP violation due to charged Higgs boson exchange. The value of $\epsilon'/\epsilon$ due to this last effect could be as large as in the standard model.Comment: 8 pages, RevTex, (appear in Phys. Rev. Lett. 73, (1994) 1762 ), CMU-HEP94-1