Exciton relaxation and level repulsion in GaAs/AlxGa1-xAs quantum wires

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Angle-resolved photoemission spectroscopy (ARPES) is a widely used characterization technique in condensed matter physics, providing direct access to the single-electron spectral function of crystals, including their electronic band structure and Fermi surface. Measuring the band structure of novel quantum materials has been fundamentally important for determining, for example, nontrivial band topology, as in topological insulators, Weyl semimetals, and Dirac semimetals, or for identifying new classes of ma

The frustrated magnet Bi2Fe4O9 has been reported to exhibit complex spin dynamics coexisting with conventional spin wave excitations. The magnetic Fe3+ (S = 5/2) ions are arranged into a distorted two-dimensional Cairo pentagonal lattice with weak couplings between the layers, developing long-ranged noncollinear antiferromagnetic order below 245 K. In order to enable studies and modeling of the complex dynamics close to TN, we have reexamined the magnetic excitations across the complete energy scale (0 < h

An iterative Finite Element method predicated on a linearization of the weak form around a reference configuration is derived for general, three-dimensional, free-surface flows, including systems with arbitrary contact angles. This sharp-interface method is a rigorous generalization of the Total Linearization Method that was proposed by Kruyt et al. (International Journal for Numerical Methods in Fluids 1988; 8: 351–363) for two-dimensional flows with contact angles limited to 90◦. In contrast to existing n

Background: The DiSCoVeR trial (The DiSCoVeR Project: Examining the synergistic effects of a cognitive control videogame and a self-administered non-invasive brain stimulation on alleviating depression) is a double-blind, sham controlled, randomized controlled trial (RCT) investigating the feasibility and efficacy of an innovative, self-applied treatment approach for patients diagnosed with major depressive disorder (MDD). The multi-site trial is conducted at three clinical trial sites (Hadassah, Isr

In this study the influence of tip leakage on the performance of a small-scale fan is evaluated through computational fluid dynamics. ANSYS CFX Release 18.1 is employed for the numerical simulations, the results are extracted, analyzed and compared to the existing literature on the subject. Having discussed the original problem geometry, the computational domain is modified to evaluate the impact of adding the diffuser on the results of the simulation.

A fundamental trait of the human self is its continuum experience of space and time. Perceptual aberrations of this spatial and temporal continuity is a major characteristic of schizophrenia spectrum disturbances – including schizophrenia, schizotypal personality disorder and schizotypy. We have previously found the classical Perceptual Aberration Scale (PAS) scores, related to body and space, to be positively correlated with both behavior and temporo-parietal activation in healthy participants performing a

We discuss the optimal evaluation of endothelial shear stress for real-life case studies based on anatomic data acquisition. The fluid dynamic simulations require smoothing of the geometric dataset to avoid major artefacts in the flow patterns, especially in the proximity of bifurcations. A systematic series of simulations at different corrugation levels shows that, below a smoothing length of about 0.5 mm, the numerical data are insensitive to further smoothing.

Apraxia is a poorly understood disorder of voluntary movement that is not due to basic sensory, motor or cognitive deficits. We conducted a study on the imitation of meaningless gestures in apraxic patients with left fronto-temporo-parietal lesions. In a first condition, the patients were instructed to imitate the orientation and position of a hand touching the face (complex task). In a second condition, the patients were instructed to solely imitate the position of contact between the face and hand, using

We experimentally investigate the effect of residual disorder on the dispersion curve of light near a band edge. A Fourier space imaging technique accurately distinguishes the propagating regime from evanescent regime in planar photonic crystal. (C) 2009 Optical Society of America

A numerical simulation of a prechamber autoignition gas engine has been performed based on an experimental test case. With a simplified finite-rate/eddy-dissipation model for the combustion of natural gas, it was possible to properly reproduce the experiment considering the combustion duration, ignition timing and overall energy balance. However the predefined empiric constant of the eddy-dissipation model had to be increased by a factor of 10. A modification of the original cylindrical-conical prechamber g

Spatially resolved photoluminescence spectra of thin GaAs quantum wells are measured by near-field spectroscopy, and two-energy autocorrelation functions of the spectra are derived. We demonstrate distinctly different autocorrelation functions for a 3-nm-thick quantum well grown on a (311)A surface and for quantum wells grown on (100) substrates. The autocorrelation spectra of the (311)A GaAs quantum well are quantitatively described by a statistical disorder model with a single correlation length of 17 nm

The structural refinement of the modulated phase of 4,4'-Diethoxyazoxybenzene (DXB) indicates a correlation between the shifts on the DXB molecule (modulation) and the probability to find the azoxy (N --> O) group in different configurations (disorder). This study shows the correlation between disorder and modulation in order to optimize the crystal packing.

Growing population, extensive use (and abuse) of the natural resources, increasing pollutants emissions in the atmosphere: these are a few obstacles (and not the least) one has to face with nowadays to ensure the sustainability of our planet in general, and of the air quality in particular. In the case of air pollution, the processes that govern the transport and the chemical transformation of pollutants are highly complex and non-linear. The use of numerical models for simulating meteorological fields, whi

We present a theoretical model of the time-resolved excitonic photoluminescence in quantum wires. We study the role of disorder and of the exciton-free-carrier interaction on the temperature dependence of the photoluminescence lifetime. We find that at low temperature the exciton population is not thermalized in disordered quantum wires and that the lifetime is mainly determined by the localization length of the exciton. However, for large localization lengths or high enough temperatures the exciton populat

Exciton states in semiconductor nanostructures with disorder exhibit level repulsion, a concept known from random matrix theory. Its manifestations in time-resolved Rayleigh spectra and in the autocorrelation of optical nearfield spectra are explained, and available experimental results are critically discussed. It is proposed to investigate the intrasubband absorption in quantum wells with emphasis on the aspects of level repulsion. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We present the results of a study of the dynamics of trions and excitons in a CdTe modulationdoped quantum well as a function of temperature in the low-density regime. Using three-pulse four-wave mixing technique, we show that, at low temperature, these quasi-particles are inhomo-geneously broadened and localized due to disorder effects. At higher temperatures, trions and excitons are mobile and their homogeneous broadening is largely increased as a result of acoustic phonon scattering. Consistently, time-r

Different measurement techniques have demonstrated that due to better alignment during the manufacturing process, the central filaments in multifilamentary Bi-2223 tapes have higher critical current density than the outer filaments. A numerical model of non-twisted tapes has been used in Finite-Element-Method simulations. The model incorporates non-uniform lateral Jc distribution in accordance with direct Ic measurements, made along the width of a Bi-2223 tape. Two types of simulations are performed on 7 an

Computer simulations of granular materials based on the distinct element method (DEM) are now commonly used in the design and optimization of industrial processes. One of the leading mathematical approach to DEM uses dynamic triangulations for detecting collisions among moving spheres, and relies on advanced data structures and on the exact numerical evaluation of computational geometry predicates. This paper outlines the simulation method and introduces the robust and adaptive computation of predicates usi

Using time-resolved photoluminescence, we have investigated the radiative behavior of neutral and negatively charged excitons in CdTe-based quantum wells. We find that the photoluminescence of negatively charged excitons can be well reproduced by a model of delocalized and thermalized three-particle complexes. A large radiative zone in k-space results from the transfer of the charged exciton momentum to the remaining electron (recoil effect). On the other hand, the photoluminescence decay of excitons is not

The fluorescence of Ag8 in an argon matrix and in argon droplets is reported. This is the first unambiguous assignment of the fluorescence of a metal cluster larger than the tetramer, indicating that the excited state lifetime is longer than previously thought. It is discussed as a possible result of a matrix cage effect. The excitation spectrum is compared with two-photon-ionization measurements of Ag8 in helium droplets and to known absorption data. The agreement is excellent. We propose that the excited

Exciton relaxation and level repulsion in GaAs/AlxGa1-xAs quantum wires

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Impact of static disorder on quasiparticle spectra: Debye-Waller, mean free path, and potential fluctuation effects

Refined Spin Hamiltonian on the Cairo Pentagonal Lattice of Bi2fe4o9

Generalization of the total linearization method to three-dimensional free-surface flows

The DiSCoVeR trial – the relationship between anxiety, depression and rumination in patients at baseline.

Blade Tio Loss in a Small-Scale Fan

Schizotypal Perceptual Aberrations of Time: Correlation between Score, Behavior and Brain Activity

Endothelial shear stress from large-scale blood flow simulations

The variability of contact position errors in apraxic imitation

Impact of the residual disorder on the slow light regime in 1D and 2D photonic crystals structures

Numerical simulations of a prechamber autoignition cogeneration engine operating on natural gas

Near-field autocorrelation spectroscopy of disordered semiconductor quantum wells

Correlation between modulation and structural disorder in the 4,4 '-diethoxyazoxybenzene

Validation and application of an urban turbulence parameterisation scheme for mesoscale atmospheric models

Modeling the photoluminescence lifetime in realistic quantum wires

Level repulsion of exciton states in disordered semiconductor nanostructures

Trions and excitons in CdTe quantum wells: Lifetimes, coherence, diffusion and localization

Numerical modelling of Bi-2223 multifilamentary tapes with position-dependent Jc

Robust 3D Dynamic Triangulations for Collision Detection in DEM Simulations of Granular Materials

Negatively charged excitons in CdTe-based quantum wells: A time-resolved study

Ag8 Fluorescence in Argon