240 research outputs found

    Incoherent charge transport through molecular wires: interplay of Coulomb interaction and wire population

    Get PDF
    The influence of Coulomb interaction on the electron transport through molecular wires is studied in the regime of incoherent tunneling. In the limit of strong Coulomb repulsion, the current for spinless electrons is determined. It is shown that the voltage profile along the wire crucially influences the dependence of the current on the wire length. Upon inclusion of the spin degree of freedom one finds a blocking effect which depends both on the interaction strength and on the population of the wire. For finite Coulomb interaction, the temperature dependence of the blocking is studied and it is shown that several regimes with different blocking strength may exist.Comment: 18 pages, 8 figures, elsart.cls v2.18 include

    Enhanced transmission through arrays of subwavelength holes in gold films coated by a finite dielectric layer

    Get PDF
    Enhanced transmissions through a gold film with arrays of subwavelength holes are theoretically studied, employing the rigid full vectorial three dimensional finite difference time domain method. Influence of air-holes shape to the transmission is firstly studied, which confirms two different resonances attributing to the enhanced transmission: the localized waveguide resonance and periodic surface plasmon resonances. For the film coated with dielectric layers, calculated results show that in the wavelength region of interest the localized waveguide resonant mode attributes to sensing rather than the periodic gold-glass surface plasmon mode. Although the detected peak is fairly broad and the shift is not too pronounced, we emphasize the contribution for sensing from the localized waveguide resonant mode, which may opens up new ways to design surface plasmon based sensors.Comment: 11 pages including 4 figures. Accepted for JEOS:R

    Performance and durability of solid oxide electrolysis cells for syngas production

    Get PDF
    Performance and durability of Ni/YSZ based solid oxide electrolysis cells (SOECs) for co-electrolysis of H2O and CO2 at high current density were investigated. The cells consist of a Ni/YSZ support, a Ni/YSZ fuel electrode, a YSZ electrolyte, and a LSM-YSZ oxygen electrode. The cell durability was examined at 800°C and electrolysis current density of -1 or -1.5 A/cm2 with 60% reactant (H2O+CO2) utilization. The cell voltage degradation showed a strong dependence on the electrolysis current density, with an overall cell voltage degradation rate of 0.24 mV/h at -1 A/cm2 and of 0.82 mV/h at -1.5 A/cm2. Electrochemical characterization of the cells showed that the degradation was mainly related to the LSM/YSZ electrode when operated at -1 A/cm2, whereas at increased current density (-1.5 A/cm2), both the Ni/YSZ and LSM/YSZ electrodes showed degradation.</jats:p

    Wave packet propagation by the Faber polynomial approximation in electrodynamics of passive media

    Full text link
    Maxwell's equations for propagation of electromagnetic waves in dispersive and absorptive (passive) media are represented in the form of the Schr\"odinger equation iΨ/t=HΨi\partial \Psi/\partial t = {H}\Psi, where H{H} is a linear differential operator (Hamiltonian) acting on a multi-dimensional vector Ψ\Psi composed of the electromagnetic fields and auxiliary matter fields describing the medium response. In this representation, the initial value problem is solved by applying the fundamental solution exp(itH)\exp(-itH) to the initial field configuration. The Faber polynomial approximation of the fundamental solution is used to develop a numerical algorithm for propagation of broad band wave packets in passive media. The action of the Hamiltonian on the wave function Ψ\Psi is approximated by the Fourier grid pseudospectral method. The algorithm is global in time, meaning that the entire propagation can be carried out in just a few time steps. A typical time step is much larger than that in finite differencing schemes, ΔtFH1\Delta t_F \gg \|H\|^{-1}. The accuracy and stability of the algorithm is analyzed. The Faber propagation method is compared with the Lanczos-Arnoldi propagation method with an example of scattering of broad band laser pulses on a periodic grating made of a dielectric whose dispersive properties are described by the Rocard-Powels-Debye model. The Faber algorithm is shown to be more efficient. The Courant limit for time stepping, ΔtCH1\Delta t_C \sim \|H\|^{-1}, is exceeded at least in 3000 times in the Faber propagation scheme.Comment: Latex, 17 pages, 4 figures (separate png files); to appear in J. Comput. Phy
    corecore