Femtosecond luminescence measurements of the intersubband scattering rate in AlxGa1-xAs/GaAs quantum wells under selective excitation

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We performed angle-resolved photoelectron spectroscopy (ARPES) and resistivity measurements on the layered metal 1T-TiTe2. We determined the quasiparticle dispersion and lifetime. In particular, we could characterize and separately evaluate the effects of the electron-electron and electron-phonon interactions on the experimental spectra. The good correlation between transport and spectroscopic scattering rates indicates that this material behaves as a model Fermi liquid system.

Space-charge effects (so-called negative-mass instability) as the reason for electron energy spread arising in the region of the electron drift between the cathode and the cavity of a gyrotron are discussed. Theoretical calculations are compared with results of measurements performed at Forschungszentrum Karlsruhe.

We present a new family of 2D orthogonal wavelets which uses quincunx sampling. The orthogonal refinement filters have a simple analytical expression in the Fourier domain as a function of the order α, which may be non-integer. The wavelets have good isotropy properties. We can also prove that they yield wavelet bases of

L _{ 2 }

(\Re ^{ 2 }

) for any α > 0. The wavelets are fractional in the sense that the approximation error at a given scale a decays like

O(a ^{ \alpha }

); they also essential

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

The nonequilibrium dynamics of a two-dimensional electron-hole gas is studied in the regime of strong and resonant pumping of the exciton resonance. The Coulomb collision rates are consistently determined by taking into account the light-induced coherence of the two-band system that leads to a dressing of the carrier spectral functions. The light dressing dramatically reduces the Coulomb scattering efficiency. Results are presented for Rabi oscillations in the time domain and dynamical Stark splitting in th

Ultrafast pump-probe measurements evidence the dynamical Stark splitting in the exciton absorption spectrum of a single semiconductor quantum well. The intensity of the Stark sidebands in the spectrum is comparable to the linear absorption and their separation scales as the pump field amplitude. In the time domain the Rabi oscillations are observed. The semiconductor Bloch equations solved in the Hartree-Fock approximation demonstrate that the coherent exciton-light coupling dominates over the many-body dep

Following the analytical description of the collisionless high-voltage capacitive RF sheath in Lieberman (1988) and of the collisional high-voltage capacitive RF sheath in Lieberman (1989), electrical sheath parameters are calculated for a square-wave ie RF discharge current. The interest in the square-wave current lies in the analytical simplicity of the solutions, The spatial dependences of the time-averaged electrostatic potential electric field (E) over bar, net-charge carrier density

We consider an electron-phonon system in two and three dimensions on square, hexagonal, and cubic lattices. The model is a modification of the standard Holstein model where the optical branch is appropriately curved in order to have a reflection positive Hamiltonian. Using infrared bounds together with a recent result on the coexistence of long-range order for electron and phonon fields, we prove that, at sufficiently low temperatures and sufficiently strong electron-phonon coupling, there is a Peierls inst

The effects of background n- and p-type doping on Zn diffusion in GaAs/AlGaAs multilayered structures are investigated by secondary-ion-mass spectrometry and photoluminescence measurements. Zn diffusions are performed at 575 degrees C into Si-doped, Be-doped, and Si/Be-codoped identical GaAs/Al0.2Ga0.8As multiple-quantum-well structures. The results obtained by secondary-ion-mass spectrometry show that the Zn diffusion induces an enhancement of Be out-diffusion and the disordering of all structures. The eff

A study of the elastic exciton-exciton Coulomb scattering in a semiconductor quantum well is presented, including the interexciton exchange of carriers and the spin degrees of freedom. The theoretical results show that electron-electron and hole-hole exchanges are the dominant mechanisms of interaction, while the classical direct term is negligible. The density-dependent homogeneous linewidth is calculated within the Born approximation and good agreement with the existing experimental data is obtained. Owin

We show that the two-dimensional quantum confined Stark effect in a semiconductor quantum wire can display novel behaviour, i.e. wave function splitting and cascading. No analog to these phenomena can be found in bulk material or quantum wells. The consequences of these effects on Stark shifts, oscillator strengths and electroabsorption spectra are explored numerically using k.p theory. A non-trivial prediction of our model is that, for the case of hole wave function splitting, the cascading of the ladder o

Experimental plasma-edge gradients in JET during the edge-localized-mode (ELM) free H-mode are examined for evidence of the presence and location of the transport barrier region inside the magnetic separatrix. High spatial resolution data in electron density is available in-and outside the separatrix from an Li-beam diagnostic, and in electron temperature inside the separatrix from an ECE diagnostic, while outside the separatrix, a reciprocating probe provides electron density and temperature data in the sc

Femtosecond luminescence measurements of the intersubband scattering rate in AlxGa1-xAs/GaAs quantum wells under selective excitation

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Quasiparticle scattering processes in a model Fermi liquid: 1T-TiTe2

On the negative-mass instability in gyrotrons

Orthogonal Quincunx Wavelets with Fractional Orders

Luminescence study of the disorder in polycrystalline InP thin films

Strongly driven exciton resonances in quantum wells: Light-induced dressing versus Coulomb scattering

Direct observation of the excitonic ac Stark splitting in a quantum well

Power laws for the spatial dependence of electrical parameters in the high-voltage capacitive RF sheath

Charge density wave and quantum fluctuations in a molecular crystal

Effects of background n- and p-type doping on Zn diffusion in GaAs AlGaAs multiple-quantum-well structures

Role of the exchange of carriers in elastic exciton-exciton scattering in quantum wells

Quantum confined Stark effect in quantum wires: Wave function splitting and cascading

Plasma-edge gradients in L-mode and ELM-free H-mode JET plasmas