Modeling the photoluminescence lifetime in realistic quantum wires

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Controlling the temporal and kinetic statistics of excitons in semiconductor nanocrystals is important for understanding how multiexcitonic processes emerge in ultrafast excited‐state dynamics under low‐fluence conditions. Under conventional single‐pulse excitation, the Poissonian nature of exciton generation limits the manifestation of biexciton‐mediated processes in the observed kinetics at low fluence. Here, we demonstrate a sequential ultrafast excitation scheme in CsPbBr 3 nanocrystals that reshapes th

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are promising materials for next-generation complementary metal-oxide-semiconductor (CMOS) technologies owing to their atomically thin channels and strong electrostatic control. Achieving the modulation of carrier polarity within a single material system is desirable for CMOS integration but remains challenging. Low-bandgap TMDCs could facilitate effective polarity tuning. Additionally, such materials provide a sensitive medium for probing doping

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

Optical excitation and control of excitonic wavepackets in organic molecules is the basis to energy conversion processes. To gain insights into such processes, it is essential to establish the relationship between the coherence timescales of excitons with the local electronic distribution in the molecules, as well as the influence of intermolecular interactions on exciton dynamics. Here, we demonstrate orbital-resolved imaging of optically induced coherent exciton dynamics in single copper naphthalocyanine

Numerous novel hole‐transporting materials (HTMs) have been reported in the literature, which play a vital role in enhancing the efficiency and stability of perovskite solar cells (PSCs). However, the PSCs using these HTMs continue to suffer from exciton recombination induced by energy level misalignment and defect states. Herein, an ingenious molecular design for HTMs ( WD03 with triphenylethylene and WD04 with trithienylethylene) is reported to modulate their energy levels and passivation effectively. The

Electron-phonon coupling is a key interaction that governs diverse physical processes such as carrier transport, superconductivity, and optical absorption. Calculating such interactions from first-principles with methods beyond density-functional theory remains a challenge. We introduce here a finite-difference framework for computing electron-phonon couplings for any electronic structure method that provides eigenvalues and eigenvectors, and showcase applications for hybrid and Koopmans functionals, and G

Zinc phosphide (Zn3P2) has been identified as a promising material for low-cost photovoltaics made of earth-abundant elements. In the 90's, the low performance of the devices based on Zn3P2 was attributed to the poor quality of the crystal. Recently, selective area epitaxy (SAE) has emerged as a method to obtain high quality materials on lattice mismatched substrates, thanks to efficient strain relaxation. Here, we study the relation between the SAE mask characteristics and the resulting optoelectronic prop

The insulating chiral magnet Cu2OSeO3 exhibits a rich array of low-temperature magnetic phenomena, making it a prime candidate for the study of its spin dynamics. Using spin wave small-angle neutron scattering (SWSANS), we systematically investigated the temperature-dependent behavior of the helimagnon excitations in the field-polarized phase of Cu2OSeO3. Our measurements, spanning 5-55 K, reveal the temperature evolution of spin-wave stiffness and damping constant with unprecedented resolution, facilitated

Advantages and remaining issues of state-of-the-art m-plane freestanding GaN (FS-GaN) substrates grown by halide vapor phase epitaxy (HVPE) for m-plane InGaN epitaxial film growth by metalorganic vapor phase epitaxy are described. Because of the low threading dislocation and basal-plane stacking fault densities, improved quantum efficiency and short radiative lifetime are achieved for the near-band-edge emission of 200–250 nm thick m-plane pseudomorphic InGaN epilayers. As the surface flatness is greatly im

The growth of GaAs nanowires by the gallium-assisted method with molecular beam epitaxy (MBE) is presented in this review article. The structure of the grown nanowires was investigated by means of scanning and transmission electron microscopy as well as Raman spectroscopy. Their optical properties were revealed by performing photoluminescence measurements at the single nanowire level. Furthermore, by tuning the MBE conditions to planar growth, quantum heterostructures on the side facets of the nanowires wer

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 motivation of this work derives from the need of the cutting tool industry to improve its products in order to support harder and harder working conditions, namely increasing cutting speeds and working on stronger modern materials. The lifetime of the tools is limited by plastic deformation that occurs at the cutting edge under working conditions, which involve high temperatures and stresses. The high temperature deformation of the materials that are used for the production of cutting tools is studied.

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.

A combined thermal and simple kinetic model is applied to a small single solid oxide fuel cell (SOFC, 20 cm2 square cell of anode supported electrolyte with 1 cm2 active area). The aim was to compute the temperature field to analyze the operating conditions of the active area of the cell. The cell is simulated in the conditions used for electrochemical characterization, i.e. at negligible fuel utilization and thermally non-adiabatic. Though using a very simple kinetic model, the simulated polarization curve

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

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 role of the confinement potential symmetry on the electronic and optical properties of quantum mires is systematically studied. In a wide class of quantum mires with mirror symmetry we evidence a new set of optical transitions resulting both from band mixing and Ct, symmetry breaking at zone center. Several kinds of quasi-one-dimensional excitons are predicted as well as their specific dipole coupling. Even for ultralow C-1 symmetry we find independent excitons with distinct polarization selection rules

Time-resolved measurements of the resonant Rayleigh scattering from quantum well excitons are shown to provide information on the energy-level statistics of the localized exciton states. The signal transients are reproduced by a microscopic quantum model of the exciton two-dimensional motion in presence of spatially correlated disorder. This model allows quantitative determination of the average energy separation between the localized states. Here this quantity turns out to be only a few times smaller than

We have performed spectral interferometry with Rayleigh scattered light coming from a single speckle and emitted after resonant creation of excitons in GaAs quantum wells:: The experiment confirms the coherence of the secondary emission at early times, regardless of sample:parameters. but underlines the stochastic nature of a single speckle. The scattered electric field is calculated, correctly accounting for the center-of-mass quantization in the disordered potential. We find that the amplitudes of the ele

We report on carrier-induced effects on emission and absorption in forward biased GaAs/AlGaAs V-groove quantum wire (QWR) diodes observed using low-temperature (10 K) photoluminescence (PL), electroluminescence (EL) and PL excitation (PLE) spectroscopy. In the case of simultaneous electron-hole injection we observe a band-gap renormalization (BGR) of at least 5 meV for a carrier density of approximate to 10(6) cm(-1), by comparing high-density EL spectra with low-density PLE spectra. In the case of electron

Modeling the photoluminescence lifetime in realistic quantum wires

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Enhanced Contribution of Biexciton‐Mediated Decay Kinetics in Perovskite Nanocrystals Via Sequential Ultrafast Excitation

Doping-Modulated Semiconductor-to-Metal Transformation in a Low-Band-Gap Two-Dimensional Material

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

Orbital-resolved imaging of coherent femtosecond exciton dynamics in coupled molecules

Reducing Interface Energy Loss of Perovskite Solar Cells by Molecular Engineering of Hole‐Transporting Materials

Carrier mobilities and electron-phonon interactions beyond DFT

Nanopatterning optimization of zinc phosphide: hole mobility up to 560 cm2/V s with selective area epitaxy

Helical spin dynamics in Cu2OSeO3 as measured with small-angle neutron scattering

Advantages and remaining issues of state-of-the-art m-plane freestanding GaN substrates grown by halide vapor phase epitaxy for m-plane InGaN epitaxial growth

GaAs nanowires and related prismatic heterostructures

Near-field autocorrelation spectroscopy of disordered semiconductor quantum wells

High temperature deformation mechanisms of cemented carbides and cermets

Level repulsion of exciton states in disordered semiconductor nanostructures

Thermal modeling of a small anode supported solid oxide fuel cell

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

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

The impact of low symmetry on the electronic and optical properties of quantum wires

Optical signatures of energy-level statistics in a disordered quantum system

Interferometric analysis of resonant Rayleigh scattering from two-dimensional excitons

Carrier-induced effects on absorption and emission in V-groove quantum wire diodes