Search results for "mesoscopic"
showing 10 items of 709 documents
Phonon-induced optical superlattice
2005
We demonstrate the formation of a dynamic optical superlattice through the modulation of a semiconductor microcavity by stimulated acoustic phonons. The high coherent phonon population produces a folded optical dispersion relation with well-defined energy gaps and renormalized energy levels, which are accessed using reflection and diffraction experiments.
Optimization of impurity profile for p-n junction in heterostructures
2005
We analyze the dopant diffusion in p-n-junction in heterostructure, by solving the diffusion equation with space-varying diffusion coefficient. For a step-wise spatial distribution we find the optimum annealing time to decrease the p-n-junction thickness and to increase the homogeneity of impurity concentration in p or n regions.
Microscopic theory for the light-induced anomalous Hall effect in graphene
2019
We employ a quantum Liouville equation with relaxation to model the recently observed anomalous Hall effect in graphene irradiated by an ultrafast pulse of circularly polarized light. In the weak-field regime, we demonstrate that the Hall effect originates from an asymmetric population of photocarriers in the Dirac bands. By contrast, in the strong-field regime, the system is driven into a non-equilibrium steady state that is well-described by topologically non-trivial Floquet-Bloch bands. Here, the anomalous Hall current originates from the combination of a population imbalance in these dressed bands together with a smaller anomalous velocity contribution arising from their Berry curvature…
EMISSION FACTORS, VEHICLE MODAL ACTIVITY AND ROAD OPERATIONS. A MESOSCOPIC APPROACH
2009
Current studies underline that vehicle emissions are highly linked to modal vehicle activity and a modal approach to traffic-related air quality modeling is suitable to estimate mobile source contribution to air quality. Pollutant emissions depend on characteristics of vehicles in traffic flow and on road operating conditions predictable after the implementation of the road project; then, the usual emission rate models do not predict properly the on-road vehicles emissions of modal traffic events, such as those ones occurring at intersections. Moreover modal activity analysis carried out at micro scale level, as required by modal emission models, will be still necessary to value reliable em…
Nonadiabatic dynamics in strongly driven diffusive Josephson junctions
2019
By measuring the Josephson emission of a diffusive Superconductor-Normal metal-Superconductor (SNS) junction at a finite temperature we reveal a non-trivial sensitivity of the supercurrent to microwave irradiation. We demonstrate that the harmonic content of the current-phase relation is modified due to the energy redistribution of quasiparticles in the normal wire induced by the electromagnetic field. The distortion originates from the phase-dependent out-of-equilibrium distribution function which is strongly affected by the ac-response of the spectral supercurrent. For phases close to $\pi$, transitions accross the Andreev gap are dynamically favored leading to a supercurrent reduction. T…
High-Temperature Hall Measurements on BaSnO3Ceramics
2005
Simultaneous Hall and conductivity measurements were performed in situ between 650° and 1050°C on n-type semiconducting BaSnO3ceramics. The variation of the Hall mobility and the Hall carrier density as a function of oxygen partial pressure between 102 and 105 Pa and of temperature was investigated. At temperatures below 900°C the conductivity exhibits a dependence on temperature and oxygen partial pressure which is mainly determined by variations of the Hall mobility. Above 900°C most of the significant dependence is due to a variation in carrier density. Furthermore, a simple defect model assuming doubly ionized oxygen vacancies and acceptor impurities is discussed for BaSnO3.
Electron scattering mechanisms inn-type indium selenide
1984
Electron scattering mechanisms in $n$-type indium selenide are investigated by means of the temperature dependence (4-500 K) of Hall mobility and the magnetic field dependence of Hall and magnetoresistance coefficients. The Schmid model for homopolar optical-phonon scattering can explain the temperature dependence of electron mobility above 40 K. The electron-phonon coupling constant is determined, ${g}^{2}=0.054$. The optical phonon involved in the process is identified as the ${A}_{1}^{\ensuremath{'}}$ phonon with energy 14.3 meV. The magnetic field dependence of Hall and magnetoresistance coefficients is discussed in terms of the Jones-Zener expansion.
Electric control of the spin Hall effect by intervalley transitions
2013
Controlling spin-related material properties by electronic means is a key step towards future spintronic technologies. The spin Hall effect (SHE) has become increasingly important for generating, detecting and using spin currents, but its strength-quantified in terms of the SHE angle-is ultimately fixed by the magnitude of the spin-orbit coupling (SOC) present for any given material system. However, if the electrons generating the SHE can be controlled by populating different areas (valleys) of the electronic structure with different SOC characteristic the SHE angle can be tuned directly within a single sample. Here we report the manipulation of the SHE in bulk GaAs at room temperature by m…
Experimental study of low-voltage surge protection device response in realistic systems
2008
Experimental results on low-voltage surge protection under fast pulses in realistic wiring systems are presented. A fast voltage pulse generator is designed to provide fast voltage pulses with short steep fronts. The effective residual voltage of protected equipment is then investigated and compared with simulation results.
The influence of Coulomb interaction screening on the excitons in disordered two-dimensional insulators.
2021
AbstractWe study the joint effect of disorder and Coulomb interaction screening on the exciton spectra in two-dimensional (2D) structures. These can be van der Waals structures or heterostructures of organic (polymeric) semiconductors as well as inorganic substances like transition metal dichalcogenides. We consider 2D screened hydrogenic problem with Rytova–Keldysh interaction by means of so-called fractional Scrödinger equation. Our main finding is that above synergy between screening and disorder either destroys the exciton (strong screening) or promote the creation of a bound state, leading to its collapse in the extreme case. Our second finding is energy levels crossing, i.e. the degen…