Determination of the exciton formation in quantum wells from time-resolved interband luminescence

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Single-photon emitters (SPEs) are promising building blocks for practical devices in quantum technologies. Traditionally, these systems are excited using off-resonant visible light through their phonon transitions, yet this process remains poorly understood. Here, we explore the interaction of mid-infrared (MIR) excitation with the properties of SPEs in hexagonal boron nitride. Notably, we present a reversible, nondestructive method to enhance emission from blue SPEs using MIR coexcitation. By resonantly dr

Phonons play an essential role in condensed matter physics, influencing key phenomena such as vibrational entropy, thermal conductivity, superconductivity, ferroelectricity, and photoluminescence spectra. Here, we present a comprehensive database of harmonic phonon properties, constructed using automated high-throughput (HT) density functional theory (DFT) calculations for 26,413 compounds. The database covers materials with all seven crystal systems and includes primitive cells with up to 60 atoms. In this

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Adiabatic Quantum Computers (AQCs) are special-purpose devices that promise to speed up the resolution of hard combinatorial optimization problems by exploiting quantum mechanical phenomena. Despite representing one of the most mature quantum computational paradigms, AQCs are often benchmarked on spin-glass problems that conveniently mimic their internal structure, and their performances are usually compared to those of suboptimal Simulated Annealing solvers. In this work, we evaluate the capabilities of AQ

"Physics-inspired" or "Quantum" Machine Learning (ML) models, that integrate physics information such as symmetry constraints and inter-atomic interaction forms, have long facilitated the accurate prediction of quantum-chemical molecular properties. While central to chemistry, related models for chemical reactions have lagged behind. This thesis takes some of the first steps in the field to establish physics-inspired reaction representations, whether constructed for use with separate ML models (e.g., kernel

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Two-dimensional (2D) materials are a new type of materials under intense study because of their interesting physical properties and wide range of potential applications from nanoelectronics to sensing and photonics. Monolayers of semiconducting transition metal dichalcogenides MoS2 or WSe2 have been proposed as promising channel materials for field-effect transistors. Their high mechanical flexibility, stability, and quality coupled with potentially inexpensive production methods offer potential advantages

The engineering of the metabolism requires the building of reliable kinetic models of the metabolic pathways through the integration of the information from heterogeneous data sources. Unfortunately, the quantitative knowledge about fluxes, mechanisms or kinetic parameters of the constituent reactions of the metabolic network is most of the times uncertain or missing, due to limitations in the measurement techniques of the relevant biological properties of the cell and variability in experimental conditions

We develop a dynamical theory for the optical injection of charge and spin current originating from the interferences between two coherent laser pulses of frequencies omega and 2omega. Multiband Bloch equations which include one- and two-photon interband transitions are derived. They also account for ac Stark shifts and intersubband two-photon transitions. The model is used to describe the case of time-dependent charge and spin current injection in a symmetric GaAs/AlGaAs quantum well. A comparison to the b

The formation mechanisms, structure and optoelectronic properties of Ga(In)As/(Al)GaAs quantum dot (QD) heterostructures grown by organometallic chemical vapor deposition on patterned (111)B GaAs substrates are reviewed. With this approach, it is possible to prepare high-quality semiconductor QDs whose position on a substrate is precisely controlled via a pre-growth photolithography step. The dots are formed at the center of an inverted, tetrahedral pyramid and are surrounded by distinct, low-dimensional ba

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The present work is devoted to the study of the dynamics of multi-photon processes in semiconductor heterostructures. A time-dependent description is important for understanding in detail the transient response of semiconductors excited by ultrashort optical pulses. In the first part of this thesis, we set up a phenomenological model based on rate equations, in order to investigate the possibility of measuring degenerate two-photon gain in a semiconductor microcavity. The amplification predicted by the mode

A novel method of controlling light absorption by exciton-polaritons is presented. The coherent light-induced coupling of excitons in multiple quantum well Bragg structures is exploited to sup press dramatically the absorption. Our results show that excitonic light absorption is not an intrinsic property of excitons but rather an extrinsic effect that occurs when the excitons dephase.

We report on time-resolved and steady-state photoluminescence studies of GaAs/AlGaAs V-groove quantum wire structures. Steady-state photoluminescence experiments are performed in the temperature range from 8 to 200 It. We evaluate the relation between photoluminescence excitation and absorption and determine experimentally the optical density in order to analyze the temperature dependence of the photoluminescence spectra. We find that, at a temperature above 60 K, the photoexcited electron-hole pairs reach

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The initial dynamics of resonantly excited secondary emission from quantum wells are dominated by Rayleigh scattering due to excitons localized in the disordered quantum well potential. We show experimentally and theoretically how the temporal shape of the early response is related to details of the two-dimensional disorder potential, and we determine the mean amplitude of the fluctuations and the correlation length. Spectral interferometry performed with a. single speckle allows to investigate the phase of

We report calculations of the electronic ground state potential energy surface (PES) of hydrogen peroxide covering, in an almost global fashion, all six internal degrees of freedom by two different ab initio techniques. Density functional theory (DFT) calculations using the Becke 3 parameter Lee-Yang-Parr (B3LYP) hybrid functional and multiconfigurational second order perturbation theory (CASPT2) calculations, both using large basis sets, are performed for a wide range of geometries (8145 DFT and 5310 CASPT

Determination of the exciton formation in quantum wells from time-resolved interband luminescence

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ll-optical Diamond Heater-Thermometer enables versatile and reliable thermal modulation of ion channels at the single-cell level

The thermodynamics of CaSiO 3 perovskite in Earth's lower mantle

Feedforward equilibrium trajectory optimization with GSPulse

An all glass, high finesse miniature integrated fiber Fabry-Perot microcavity produced by 3D femtosecond laser processing

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169 Bedload tranport rate fluctuations in a flume with a lternate bars under steady state conditions.

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A Highly Stable Gadolinium Complex with a Fast, Associative Mechanism of Water Exchange

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Is light absorption by excitons in quantum wells an intrinsic process?

Photoluminescence study of V-groove quantum wires: The influence of disorder on the optical spectra and the carrier thermalization

Evaluation of solubility parameters during polymerisation of amine-cured epoxy resins

Excitonic dephasing effects studied by time- and phase-resolved secondary emission

A new six-dimensional analytical potential up to chemically significant energies for the electronic ground state of hydrogen peroxide