Gate-controllable spin-battery

We propose a gate-controllable spin-battery for spin current. The spin-battery consists of a lateral double quantum dot under a uniform magnetic field. A finite DC spin-current is driven out of the device by controlling a set of gate voltages. Spin-current can also be delivered in the absence of charge-current. The proposed device should be realizable using present technology at low temperature.Comment: 3 pages, 3 figures, accepted by Appl. Phys. Let

Universal spin-Hall conductance fluctuations in two dimensions

We report a theoretical investigation on spin-Hall conductance fluctuation of disordered four terminal devices in the presence of Rashba or/and Dresselhaus spin-orbital interactions in two dimensions. As a function of disorder, the spin-Hall conductance $G_{sH}$ shows ballistic, diffusive and insulating transport regimes. For given spin-orbit interactions, a universal spin-Hall conductance fluctuation (USCF) is found in the diffusive regime. The value of the USCF depends on the spin-orbit coupling $t_{so}$, but is independent of other system parameters. It is also independent of whether Rashba or Dresselhaus or both spin-orbital interactions are present. When $t_{so}$ is comparable to the hopping energy $t$, the USCF is a universal number $\sim 0.18 e/4\pi$. The distribution of $G_{sH}$ crosses over from a Gaussian distribution in the metallic regime to a non-Gaussian distribution in the insulating regime as the disorder strength is increased.Comment: to be published in Phys. Rev. Lett., 4 figure

Nonlinear transport theory for hybrid normal-superconducting devices

We report a theory for analyzing nonlinear DC transport properties of mesoscopic or nanoscopic normal-superconducting (N-S) systems. Special attention was paid such that our theory satisfies gauge invariance. At the linear transport regime and the sub-gap region where the familiar scattering matrix theory has been developed, we provide confirmation that our theory and the scattering matrix theory are equivalent. At the nonlinear regime, however, our theory allows the investigation of a number of important problems: for N-S hybrid systems we have derived the general nonlinear current-voltage characteristics in terms of the scattering Green's function, the second order nonlinear conductance at the weakly nonlinear regime, and nonequilibrium charge pile-up in the device which defines the electrochemical capacitance coefficients

Research on IFR of Technological Evolution Bifurcations

AbstractIdealization is a powerful tool in TRIZ, and it plays an important role in innovation processes. In the fierce market competition, in order to adopt new technology and make their product approach to ideal product, enterprises spare no effort to improve the degree of product's idealization. At the bifurcation points of product technology evolution, the ideal result that customers need changes, but because of the existence of conventional thinking and market competition, engineers always engage in designing according to the original target ideal result, finally the technology innovation opportunities are lost, so it is of great significance to study the Ideal Final Result (IFR) at the bifurcation points. According to different innovation processes of S-curves, the IFR for product's technology evolution bifurcations are divided into four classifications, Incremental Innovation Ideal Final Result(IFR_II), Radical Innovation Ideal Final Result(IFR_RI), Low-end Disruptive Innovation Ideal Final Result(IFR_LDI) and New-market Disruptive Innovation Ideal Final Result(IFR_NDI). Product's technology system consists of several technology sub-systems, correspondingly, ideal product is made up of several idealized technology sub-systems. It is the objective of product design that realizing the idealization of technology subsystem through innovation design, however, because the presence of conflicts and design constraints among technology sub-systems, the design aim for realizing ideal final results of each sub-system is almost impossible. Therefore, in designing processes, engineers always give priority to several mainstream technology sub-systems and realize their idealization first. This paper decomposes IFR into several ideal results of sub-systems based on a technical system decomposition method, researches a process of technology evolution and a changing process of sub-systems’ ideal results, determines evolution bifurcations’ direction of technology systems through the combination of the sub-systems’ ideal results and then realizes the technology forecasting at the evolution bifurcation points

A spin-cell for spin current

We propose and investigate a spin-cell device which provides the necessary spin-motive force to drive a spin current for future spintronic circuits. Our spin-cell have four basic characteristics: (i) it has two poles so that a spin current flows in from one pole and out from the other pole, this way a complete spin-circuit can be established; (ii) it has a source of energy to drive the spin current; (iii) it maintains spin coherence so that a sizable spin current can be delivered; (iv) it drives a spin current without a charge current. The proposed spin-cell for spin current should be realizable using technologies presently available.Comment: 7 pages, 3 figure