Magnetic-field effects in the luminescence of V-shaped quantum wires

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Recently, engineering return stroke models were extended to take into account the presence of an elevated strike object, which was modeled as an ideal uniform transmission line. We show in this paper that the current distribution associated with these extended models exhibits a discontinuity at the return stroke wave front, which cannot be considered to be physically plausible. This discontinuity arises from the fact that the current injected into the tower from its top is reflected back and forth at its en

The aim of this thesis work is to study the spin-dependent transport in multiwalled carbon nanotubes (MWNT). To do so, the electrical resistance of MWNT contacted between ferromagnetic electrodes has been measured, as a function of the contacts magnetic configuration and temperature. An original sample fabrication process to contact MWNT has been developed. The MWNT growth is achieved via chemical vapour deposition in the pores of an alumina template, with electrodeposited nickel or cobalt nanowires as cata

We investigate in this paper a numerical method to control the temperature of an induction heating process through electric current parameters such as frequency and current voltage imposed to the terminals of the inductor. We seek a sinusoidal voltage function whose amplitude varies in time. For this, we use a two-dimensional induction heating model. that involves a phase transition in which the magnetic field has only one nonvanishing component. The procedure can be extended to more sophisticated models wi

We have studied systems of asymmetric coupled GaAs V-groove quantum wires p-i-n diodes, in which the electrons and holes are injected into different wires. Despite the use of a 7 nm thick AlGaAs tunnel barrier, and although we demonstrate that holes tunnel more slowly than electrons, we observe a very efficient and fast tunneling between the quantum wires (QWR's). We attribute this to the achievement of a resonance between hole levels in the two QWR's. Photoluminescence excitation experiments are compared w

We present detailed analysis of inter- and intraband transitions in GaN/AlN self-organized quantum dots grown on sapphire, silicon (111) and 6H-SiC substrates. Samples containing quantum dots of different size were characterized by means of transmission electron microscopy, photoluminescence and photoinduced absorption spectroscopy. Interlevel transitions in the conduction band were identified in the 0.52-0.98 eV range covering the telecommunication wavelength band. The s-p(z), transition ranges from 0.52 e

We analyze the magnitude of degenerate two-photon gain of several quantum wells (QWs) in a resonant microcavity which is pumped off-resonantly by an optical field. A set of coupled phenomenological rate equations for electron-hole pairs and photons is derived. In the framework of this model, we make a realistic prediction of the time-integrated two-photon gain and find that a lambda-cavity containing 11 QWs would give a maximal amplification of similar to 2.3% for a peak,intensity of similar to 80 MW/cm(2).

This paper describes quantitatively the influence of the self-field and the cross-sectional geometry on the effective critical current and the ac losses in transport current applications of non-twisted multifilamentary Bi-2223/Ag conductors. The results are obtained with finite element method simulations. The numerical implementation includes an anisotropic model for the dependence of the critical current density Jc and the power index n on the local parallel and perpendicular magnetic field components. The

The possibility of fulfilling the condition of poloidal closure of the contours of the second adiabatic invariant for all reflected particles is studied for systems with poloidally closed contours of the magnetic field B on the magnetic surfaces through computational stellarator optimization. It is shown that by adjusting the geometry this is possible in a major fraction of the plasma volume. The most salient characteristic (as compared to previous quasi-isodynamic configurations) is a magnetic axis whose c

One view of the high-transition-temperature (high-T-c) copper oxide superconductors is that they are conventional superconductors where the pairing occurs between weakly interacting quasi-particles (corresponding to the electrons in ordinary metals), although the theory has to be pushed to its limit(1). An alternative view is that the electrons organize into collective textures (for example, charge and spin stripes) which cannot be 'mapped' onto the electrons in ordinary metals. Understanding the properties

Fully kinetic assessments of the stability properties of toroidal drift modes have been obtained for cases for the large helical device (LHD). This calculation employs the comprehensive linear microinstability code FULL, as recently extended for nonaxisymmetric systems. The code retains the important effects in the linearized gyrokinetic equation, using the lowest-order 'ballooning representation' for high toroidal mode number instabilities in the electrostatic limit. These effects include trapped particles

InP films have been deposited on amorphous sapphire substrate by means of the metallorganic chemical vapour deposition technique with and without PH3/H-2 plasma preactivation. Polycrystalline materials, having average grain sizes of about 40 nm, which, however, vary according to the growth parameters, were obtained. The structural and compositional disorder strongly influence the optical and electrical properties. The most structurally disordered films present the largest photoluminescence (PL) efficiency a

We report on X-ray photoemission of core levels, valence band studies using angle-integrated photoemission, and magnetization measurements of ruthenocuprate and SrRuO3 polycrystalline samples. The data indicate that the RuO2 planes are the source of the energetics of the magnetic ordering. We also find that adding hydrogen leads to changes in the many-body response on both the CuO2 and EuO planes.

Magnetic-field effects in the luminescence of V-shaped quantum wires

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Electromagnetic field radiated by lightning to tall towers: treatment of the discontinuity at the return stroke wave front

Longueur de diffusion de spin et magnétisme de structures nanotubes de carbone / matériaux ferromagnétiques

Optimal control of an induction heating process for thixoforming

Electroluminescence and photoluminescence excitation study of asymmetric coupled GaAs/AlxGa1-xAs V-groove quantum wires

Spectroscopy of the electron states in self-organized GaN/AlN quantum dots

Feasibility study for degenerate-two-photon gain in a semiconductor microcavity

Self-field and geometry effects in transport current applications of multifilamentary Bi-2223/Ag conductors

Improved alpha-particle confinement in stellarators with poloidally closed contours of the magnetic field strength

Antiferromagnetic order induced by an applied magnetic field in a high-temperature superconductor

Microinstability studies for the large helical device

Luminescence study of the disorder in polycrystalline InP thin films

Electronic and magnetic properties of ruthenocuprates