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The oxygen adsorption and dissociation on pristine silicene surface are studied by use of first-principles in this letter. The oxygen adsorption and dissociation on pristine silicene surface are studied by use of first-principles in this letter. It is found that the pristine silicene is not stable in air because the oxygen molecule can be easily adsorbed and dissociated into two O atoms without overcoming any energy barrier on pristine silicene surface. In addition, dissociated oxygen atoms are relatively difficult to migrate on or desorbed from pristine silicene surface, leading to poor mobility of oxygen atom. As a result, silicene would be changed into Si-O compounds in air. The work will be helpful to reveal the detail of the interaction between oxygen molecules and pristine silicene surface, especially helpful to understand the stability of silicene in air.

Considering screeening of electron scattering interactions in terms of the finite-temperature STLS theory and solving the linearized Boltzmann equation (with no appeal to a relaxation time approximation), we present a theoretical analysis of the low-temperature Seebeck effect in two-dimensional semiconductors with dilute electron densities. We find that the temperature ($T$) dependencies of the diffusion and phonon-drag thermoelectric powers ($S_d$ and $S_g$) can no longer be described by the conventional simple power-laws. As temperature increases, $|S_d|/T$ decreases when $T\gtrsim 0.1 \epsilon_F$ ($\epsilon_F$ is the Fermi energy), while $|S_g|$ first increases and then falls, resulting a peak located at a temperature between Bloch-Gr\"uneisen temperature and $\epsilon_F$., Comment: 12 pages, 5 figures

The frequency dependence of the peak-valley pairs occurring in the magnetoresistivity of a two-dimensional electron system under enhanced microwave irradiation, which are considered to associate with multiphoton processes, is examined in the sub-cyclotron-frequency range, based on a theoretical treatment with photon-assisted electron transitions due to impurity scattering. It is shown that with equivalent radiation power (producing the same height of the main oscillation peak), much more and stronger multi-photon structures show up at lower frequency, and when frequency increases all these structures rapidly weaken, diminish and finally disappear completely. These are in agreement with the recent experimental observation [cond-mat/0608633]., 2 pages, 2 figures

In some theoretical analyses of microwave-induced magnetoresistance oscillations in high-mobility two-dimensional systems, the "inelastic relaxation time" $\tau_{in}$ due to electron-electron scattering is evaluated using an equilibrium distribution function $f^0$ in the absence of radiation, and it is concluded that $\tau_{in}$ is much larger than $\tau_{q}$, the single-particle relaxation time due to impurity scattering. However, under the irradiation of a microwave capable of producing magnetoresistance oscillation, the distribution function of the high-mobility electron gas deviates remarkably from $f^0$ at low temperatures. Estimating $\tau_{in}$ using an approximate nonequilibrium distribution function rather than using $f^0$, one will find the system to be in the opposite limit $1/\tau_{in}\ll 1/\tau_{q}$ even for T=0 K. Therefore, models which depend on the assumption $1/\tau_{in}\gg 1/\tau_{q}$ may not be justifiable., Comment: 1 page

We employ a quantum Langevin equation approach to establish non-Markovian dynamical equations, on a fully microscopic basis, to investigate the measurement of the state of a coupled quantum dot qubit by a nearby quantum point contact. The ensuing Bloch equations allow us to examine qubit relaxation and decoherence induced by measurement, and also the noise spectrum of meter output current with the help of a quantum regression theorem, at arbitrary bias-voltage and temperature. Our analyses provide a clear resolution of a recent debate concerning the occurrence of a quantum oscillation peak in the noise spectrum., Comment: 5 pages, 3 figures, submitted, published version in Phys. Rev. B

We propose a nonequilibrium Green's function approach to study the spin-Hall effect in a two-dimensional electron system with both the Rashba and Dresselhaus spin-orbit couplings. By taking into account the long-range electron-impurity scattering, the derived kinetic equations are solved numerically. It is found the vanishing of the total zero-temperature dissipationless spin-Hall effect, contributing from the intrinsic and disorder-mediated processes. This result has been examined in the wide ranges of spin-orbit coupling constants and electron density., Comment: 5 pages, 1 figure

A nonequilibrium Green's functions approach to spin-Hall effect is developed in a diffusive two-dimensional electron system with Rashba spin-orbit interaction. In the presence of long-range impurities, the coupled quantum kinetic equations are solved analytically in the self-consistent Born approximation. It is shown that the intrinsic spin-Hall effect stems from the dc-field-induced perturbation of the density of states. In addition, there is an additional disorder-mediated process, which involves the transition of nonequilibrium electrons between two spin-orbit-coupled bands. It results in an additional collision-independent spin-Hall conductivity and leads to the vanishing of the total spin-Hall current even at nonzero temperature., mistakes in references and formulas corrected

It is shown that, although the major feature of the microwave-induced magnetoresistance oscillations in two-dimensional (2D) electron systems is insensitive to the behavior of the elastic scattering in the photon-assisted impurity scattering model [X.L. Lei and S.Y. Liu, Phys. Rev. Lett. 91, 226805 (2003)], the required microwave intensity to induce an effective oscillation depends strongly on the form of the impurity potential. A microwave electric field of a few Volts per cm in amplitude is sufficient to induce remarkable oscillations if the elastic scatterings are due to background charged impurities, which is an order of magnitude smaller than that needed if the scatterings are due to remote charged impurities located 60 nm away from 2D electron gas.

We present a detailed theoretical investigation on the radiation induced giant magnetoresistance oscillations recently discovered in high-mobility two-dimensional electron gas. Electron interactions with impurities, transverse and longitudinal acoustic phonons in GaAs-based heterosystems are considered simultaneously. Multiphoton-assisted impurity scatterings are shown to be the primary origin of the resistance oscillation. Based on the balance-equation theory developed for magnetotransport in Faraday geometry, we are able not only to reproduce the observed period, phase and the negative resistivity of the main oscillations, but also to predict the secondary peak/valley structures relating to two-photon and three-photon processes. The dependence of the magnetoresistance oscillation on microwave intensity, the role of dc bias current and the effect of elevated electron temperature are discussed. Furthermore, we propose that the temperature-dependence of the resistance oscillation stems from the growth of the Landau level broadening due to the enhancement of acoustic phonon scattering with increasing lattice temperature. The calculated temperature-variation of the oscillation agrees well with experimental observations., 11 pages with 8 figures

This paper has been withdrawn by the author(s), Comment: 4 papes, 6 figures