Generation of spin current and polarization under dynamic gate control of spin-orbit interaction in low-dimensional semiconductor systems

Based on the Keldysh formalism, the Boltzmann kinetic equation and the drift diffusion equation have been derived for studying spin polarization flow and spin accumulation under effect of the time dependent Rashba spin-orbit interaction in a semiconductor quantum well. The time dependent Rashba interaction is provided by time dependent electric gates of appropriate shapes. Several examples of spin manipulation by gates have been considered. Mechanisms and conditions for obtaining the stationary spin density and the induced rectified DC spin current are studied.Comment: 10 pages, 3 figures, RevTeX

Strain-Induced Coupling of Spin Current to Nanomechanical Oscillations

We propose a setup which allows to couple the electron spin degree of freedom to the mechanical motions of a nanomechanical system not involving any of the ferromagnetic components. The proposed method employs the strain induced spin-orbit interaction of electrons in narrow gap semiconductors. We have shown how this method can be used for detection and manipulation of the spin flow through a suspended rod in a nanomechanical device.Comment: 4 pages, 1 figur

DC Spin Current Generation in a Rashba-type Quantum Channel

We propose and demonstrate theoretically that resonant inelastic scattering (RIS) can play an important role in dc spin current generation. The RIS makes it possible to generate dc spin current via a simple gate configuration: a single finger-gate that locates atop and orients transversely to a quantum channel in the presence of Rashba spin-orbit interaction. The ac biased finger-gate gives rise to a time-variation in the Rashba coupling parameter, which causes spin-resolved RIS, and subsequently contributes to the dc spin current. The spin current depends on both the static and the dynamic parts in the Rashba coupling parameter, $\alpha_0$ and $\alpha_1$, respectively, and is proportional to $\alpha_0 \alpha_1^2$. The proposed gate configuration has the added advantage that no dc charge current is generated. Our study also shows that the spin current generation can be enhanced significantly in a double finger-gate configuration.Comment: 4 pages,4 figure

Observational and theoretical studies of the evolving structure of baroclinic waves

Dynamical processes involved in comma cloud formation, and passive tracer evolution in a baroclinic wave are discussed. An analytical solution was obtained demonstrating the complex nongeostrophic flow pattern involved in the redistribution of low level constituents in a finite amplitude baroclinic wave, and in the formation of the typical humidity and cloud distributions in such a wave. Observational and theoretical studies of blocking weather patterns in middle latitude flows were studied. The differences in the energy and enstrophy cascades in blocking and nonblocking situations were shown. It was established that pronounced upscale flow of both of these quantities, from intermediate to planetary scales, occurs during blocking episodes. The upscale flux of enstrophy, in particular, suggests that the persistence of blocking periods may be due to reduced dissipation of the large scale circulation and therefore entail some above normal predictability

Representation of SO(3) Group by a Maximally Entangled State

A representation of the SO(3) group is mapped into a maximally entangled two qubit state according to literatures. To show the evolution of the entangled state, a model is set up on an maximally entangled electron pair, two electrons of which pass independently through a rotating magnetic field. It is found that the evolution path of the entangled state in the SO(3) sphere breaks an odd or even number of times, corresponding to the double connectedness of the SO(3) group. An odd number of breaks leads to an additional $\pi$ phase to the entangled state, but an even number of breaks does not. A scheme to trace the evolution of the entangled state is proposed by means of entangled photon pairs and Kerr medium, allowing observation of the additional $\pi$ phase.Comment: 4 pages, 3 figure