Rectangular Quantum Research Articles

Optical anisotropy of high-order harmonic generation by strong laser radiation in rectangular graphene quantum dot

Optical anisotropy of high-order harmonic generation by strong laser radiation in rectangular graphene quantum dot

Modeling Temperature Dependence of The Combined Density of States in Heterostructures with Quantum Wells Under the Influence of a Quantizing Magnetic Field

In this work, the dependence of the oscillation of the combined density of states on a strong magnetic field in heterostructures based on a rectangular quantum well is studied. The effect of a quantizing magnetic field on the temperature dependence of the combined density of states in nanoscale straight-band heterostructures is investigated. A new mathematical model has been developed for calculating the temperature dependence of the two-dimensional combined density of quantum well states in quantizing magnetic fields. The proposed model explains the experimental results in nanoscale straight-band semiconductors with a parabolic dispersion law.

The Impact of a Strong Electromagnetic Wave on the Quantum Hall Effect in Cylindrical Quantum Wires

The impact of strong electromagnetic waves Hall effect is studied theoretically in a Cylindrical Quantum Wire (CQW) with infinitely high potential inside the wire and elsewhere subjected to a dc electric field , a magnetic field and a laser radiation . By using the quantum kinetic equation method for electrons interacting with Acoustic Phonon (AP) at low temperatures, we obtain analytical expressions for the conductivity tensor and the Hall Coefficient (HC), which are different from in comparison to those obtained for a rectangular quantum wire (RQW) or two-dimensional (2D) electron systems. Numerical calculations are also applied for GaAs/GaAsAl CQW to show the nonlinear dependence of the HC on the electromagnetic wave (EMW) frequency, and the radius, the length characteristic parameters of CQW. Wave function and energy spectrum in a CQW are dissiminar to those in Quantum Wires (QWs). Therefore, all numerical results are different from those in the case of QWs. The most important result is that the HC reaches saturation as the radius, the length of CQW or the EMW frequency increases.

Controllable spin transport in a zigzag silicene nanoribbon embedding multiple rectangular quantum dots

Based on the recursive Green-function method together with Landauer–Büttiker formalism, the spin-dependent transport properties of electrons in a zigzag silicene nanoribbon embedding multiple rectangular quantum dots (QDs) are investigated. According to an analysis of the energy band under the periodically distributed electric field and exchange ferromagnetic field, the parallel exchange field induced by the ferromagnetic insulators eliminates the spin degeneracy, which leads to spin-polarized transport in the proposed structure. By tuning a periodic electric field, we found the relationship between the number of QDs and the splitting peak for conductance in the anti-parallel exchange field. We discover the population of electrons near QDs by calculating the local density of states. The effect of the geometry of periodic QDs on the shift of resonance peak is evaluated. The spin polarization is further explored for various configurations of electric field and exchange field in order to manipulate the spin filtering more effectively. The results provide an avenue to design a controllable spin bandpass filter with the modulation of electric field and exchange field.

Excitation and control of level populations in rectangular quantum wells by unipolar half-cycle attosecond pulses

Unipolar and quasi-unipolar half-cycle pulses represent the limit of the pulse shortening in a given spectral range. So far such pulses have become a subject of active research due to their potential in the ultrafast optics and study of new regimes of light–matter interactions with subcycle resolution. Here, we show the possibility of the effective ultrafast control of the level populations in 1D rectangular quantum wells (such a model is used for modeling semiconductor nanostructures and nanoparticles) by the half-cycle unipolar attosecond light pulses in comparison to the single-cycle ones. It is shown that the population dynamics is determined by the electric pulse area divided into its characteristic “scale,” which is given by the quantum well width when pulse duration is smaller than the orbital period of electrons in the ground state. Both the selective excitation of quantum states and the feasibility of the population inversion by subcycle unipolar pulses are demonstrated.

Effects of parabolic barrier design for multiple GaAsBi/AlGaAs quantum well structures

The results of a comparative study on how the design of multiple quantum structures containing a parabolic barrier profile affects optical properties are presented. All quantum well (QW) structures were grown by molecular beam epitaxy (MBE) on semi-insulating GaAs substrates. The investigated samples consisted of (i) double parabolic quantum wells (type A) or (ii) multiple (two or three) rectangular quantum wells surrounded by parabolic barriers (type B). The optical quality of samples was characterized performing room-temperature (RT-PL) and temperaturedependent photoluminescence (TD-PL) measurements. The investigation aimed at the optimization of a multiple quantum well (MQW) structure design for application in the gain region of near infrared (NIR) laser diodes (LDs) revealed benefits of both double parabolic quantum wells and a mixed design (rectangular MQW with parabolic barriers). The PL band position for all samples was registered in the vicinity around 1.19 eV, which corresponds to the Bi content in QW of ~4.4%. It was shown that all structures of type A exhibit an intense emission, while the intensity of photoluminescence measured for the samples of type B depends on the number of QWs. The weaker intensity of the PL signal from two QWs inserted between parabolic barriers was explained by a larger point defect density at low temperature grown inner GaAs barriers. The room-temperature PL intensity of the structure with three GaAsBi QWs embedded in one parabolic AlGaAs barrier was the highest one. The shift of PL peak position to lower energies (1.16 eV) was attributed to the slightly higher bismuth concentration, 4.9%.

The exotic behavior of the wave evolution in Lévy crystals within a fractional medium

We investigate a traveling Gaussian wave packet transport through a rectangular quantum barrier of lévy crystals in fractional quantum mechanics formalism. We study both standard and fractional Schrödinger equations in linear and nonlinear regimes by using a split-step finite difference (SSFD) method. We evaluate the reflection, trapping, and transmission coefficients of the wave packet and the wave packet spreading by using time-dependent inverse participation ratio (IPR) and second moment. By simultaneously adjusting the fractional and nonlinear terms, we create sharp pulses, which is an essential issue in optoelectronic devices. We illustrate that the effects of barrier height and width on the transmission coefficient are strangely different for the standard and fractional Schrödinger equations. We observe fortunately soliton-like localized wave packets in the fractional regime. Thus, we can effectively control the behavior of the wave evolution by adjusting the available parameters, which can excite new ideas in optics.

Determination of the Dependence of the Oscillation of Transverse Electrical Conductivity and Magnetoresistance on Temperature in Heterostructures Based on Quantum Wells

In this work, the influence of two-dimensional state density on oscillations of transverse electrical conductivity in heterostructures with rectangular quantum wells is investigated. A new analytical expression is derived for calculating the temperature dependence of the transverse electrical conductivity oscillation and the magnetoresistance of a quantum well. For the first time, a mechanism has been developed for oscillating the transverse electrical conductivity and magnetoresistance of a quantum well from the first-order derivative of the magnetic field (differential) at low temperatures and weak magnetic fields. The oscillations of electrical conductivity and magnetoresistance of a narrow-band quantum well with a non-parabolic dispersion law are investigated. The proposed theory investigated the results of experiments of a narrow-band quantum well (InxGa1-xSb).

Simulation of temperature dependence of oscillations of longitudinal magnetoresistance in nanoelectronic semiconductor materials

In this work, the influence of two-dimensional state density on oscillations of transverse electrical conductivity in heterostructures with rectangular quantum wells is investigated. A new analytical expression is derived for calculating the temperature dependence of the transverse electrical conductivity oscillation and the magnetoresistance of a quantum well. For the first time, a mechanism has been developed for oscillating the transverse electrical conductivity and magnetoresistance of a quantum well from the first-order derivative of the magnetic field (differential) ∂(ρ⊥2d(E,B,T,d))∂B at low temperatures and weak magnetic fields. The oscillations of electrical conductivity and magnetoresistance of a narrow-band quantum well with a non-parabolic dispersion law are investigated. The proposed theory investigated the results of experiments of a narrow-band quantum well (InxGa1-xSb).

Influence of the two-dimensional density of states on the temperature dependence of the electrical conductivity oscillations in heterostructures with quantum wells

In this work, the influence of two-dimensional state density on oscillations of transverse electrical conductivity in heterostructures with rectangular quantum wells is investigated. A new analytical expression is derived for calculating the temperature dependence of the transverse electrical conductivity oscillation and the magnetoresistance of a quantum well. For the first time, a mechanism has been developed for oscillating the transverse electrical conductivity and magnetoresistance of a quantum well from the first-order derivative of the magnetic field (differential) [Formula: see text] at low temperatures and weak magnetic fields. The oscillations of electrical conductivity and magnetoresistance of a narrow-band quantum well with a nonparabolic dispersion law are investigated. The proposed theory investigated the results of experiments of a narrow-band quantum well (InxGa[Formula: see text]Sb).

Formation of the stopped polarization pulse in a rectangular quantum well

The induced polarization oscillations in a one-dimensional rectangular quantum well are modeled by a numerical solution of the time-dependent Schrödinger equation. The finite-difference discretization over time is realized in the framework of the Crank-Nicolson algorithm, whereas over the spatial coordinate it is combined with the exterior complex-scaling technique. A formation of the harmonic oscillations of the dipole moment by an incident short unipolar pulse is shown. It is obtained that the frequency of oscillations is solely defined by the energy of the main resonant transition. Moreover, if two such short unipolar pulses are delayed by a half-period of the oscillation, then these oscillations can be abruptly induced and stopped. Thus, the so-called stopped polarization pulse is obtained. It is shown that both the amplitude and the duration of the incident unipolar pulse, contributing to the so-called electric pulse area, define the impact of the incident pulse on the quantum system.

Calculation of parallel Peltier coefficient in rectangular quantum wires under the influence of confined optical phonons and electromagnetic waves using quantum kinetic equation

Calculation of parallel Peltier coefficient in rectangular quantum wires under the influence of confined optical phonons and electromagnetic waves using quantum kinetic equation

Energy Quantization in Rectangular Quantum Dots

Energy Quantization in Rectangular Quantum Dots

Multiphoton excitation and high harmonic generation in rectangular graphene quantum dot

The multiphoton excitation and high harmonic generation (HHG) processes are considered using the microscopic quantum theory of nonlinear interaction of strong coherent electromagnetic (EM) radiation with rectangular graphene quantum dot (RGQD). The dynamic Hartree–Fock approximation is developed for the consideration of the quantum dot-laser field nonlinear interaction at the nonadiabatic multiphoton excitation regime. The many-body Coulomb interaction is described in the extended Hubbard approximation. By numerical results, we show the significance of the RGQD lateral size, shape, and EM wavefield orientation in RGQD of the zigzag edge compear to the armchair edge in the HHG process allowing for increasing the cutoff photon energy and the quantum yield of higher harmonics. The differences via edge on the elongated side of the RGQD have been explained by the investigation of the dipole momentum in both cases. Numerical results have shown that the HHG spectra have a strong anisotropy depending on the orientation of the laser wave, and the cutoff photon energy shifts toward blue with an increase in the transverse size of the RGQD.

Effect of Confined Optical Phonons on Photo-Stimulated Ettingshausen Effect in Rectangular Quantum Wires with A Perpendicular Magnetic Field

We applied the quantum kinetic equation method to investigate the influence of confined optical phonons (confined OP) on the photo-stimulated Ettingshausen effect in rectangular quantum wires (RQW) subjected to a perpendicular magnetic field. We considered the case where the confined electrons-confined OP scattering is the dominant mechanism. Analytical expressions for the kinetic tensors, the EC are obtained. The EC is a function of external fields, the temperature of the system, especially the quantum numbers m1 and m2 characterizing confined OP. When the width of the wire increases to infinity, the results of the bulk semiconductors can be gained. The numerical results are numerically evaluated and discussed for the GaAs/AlGaAs RQW. The magnitude of the resonance peaks has been increased for each value of m1, m2, found when examining the dependence of the EC on the photon energy. Furthermore, the EC is decreased considerably when the amplitude of EMW increases, which is obtained when investigating the dependence of the EC on the amplitude of EMW (laser). These results are important for further researches and could be helped to complete the theory of the thermo - magnetoelectric effects in the low dimensional system.
 

Energy spectrum and light absorption of arsenene quantum dots

As a close relative of phosphorene, puckered arsenene is stable and has been demonstrated experimentally as a promising two-dimensional semiconductor material. By means of a multi-orbital tight-binding model, we investigate theoretically the energy spectrum and magneto-optical properties of circular and rectangular arsenene quantum dots (AQDs). The tight-binding parameters are obtained by reproducing accurately the electron energy bands of puckered arsenene from the first-principle calculation. For both AQDs, the density of states (DOS), probability distribution and inverse participation ratio (IPR) of eigenstates, and optical absorption spectrum are calculated numerically. It is found that edge states of AQDs fill up the bulk band gap of puckered arsenene and are only localized near the armchair edges of AQDs. These features differ greatly from those in quantum dots made of graphene or phosphorene. The band edges of arsenene monolayer can be located roughly from the IPR and DOS spectrum. The light absorptivity of both AQDs under zero magnetic field depends strongly on the polarization direction of incident light. The position and intensity of absorption peaks can be tuned by the shape of quantum dots and the applied magnetic field. The anisotropy ratio of light absorption can be reduced by one order of magnitude under a magnetic field of tens of Tesla.

Coherent Control and Creation of Population Gratings for a Pair of Attosecond Pulses in a Resonant Medium Based on One-Dimensional Rectangular Quantum Wells

Coherent Control and Creation of Population Gratings for a Pair of Attosecond Pulses in a Resonant Medium Based on One-Dimensional Rectangular Quantum Wells

Temperature dependence of width band gap in Inxga1-Xasquantum well in presence of transverse strong magnetic field

This article investigated the temperature dependence of the width band gap in InxGa1-xAs quantum well in the presence of a transverse strong magnetic field. A new method was proposed for determining the width band gap of GaAs/InxGa1-xAs heterostructures based on a InxGa1-xAs quantum well in the presence of a magnetic field and temperature. An analytical expression is obtained for calculating the width band gap of a rectangular quantum well at various magnetic fields and temperatures.

Peculiarities of Excitation of a Particle in a Single-Level Quantum Well by an Extremely Short Attosecond Pulse

Using the solution of the time-dependent Schrodinger equation, the features of the excitation of a bound state of a particle in a one-dimensional rectangular quantum well of small depth by an extremely short light pulse are studied. The case of a shallow well with only one energy level is considered. In this case, the system is excited by an attosecond pulse whose duration is shorter than the characteristic time associated with the energy of the bound state of the particle in the well. It is shown that in this case the population of the bound state and the ionization probability are determined by the ratio of the electric area of the pulse to its atomic scale, which is inversely proportional to the well width. The calculation results showed that unipolar subcycle pulses with nonzero electric area can excite the system faster and more efficiently than bipolar pulses with zero area. The possibility of using unipolar gamma-ray pulses of zeptosecond duration for deuteron excitation is discussed, and numerical estimates of the required duration and electric area of the pulse are given. Keywords: extremely short pulses attosecond pulses, unipolar pulses, electric area of a pulse, atomic scale of electric area, one-dimensional quantum wells, nanostructures.

Особенности возбуждения частицы в одноуровневой квантовой яме предельно коротким аттосекундным импульсом

Using the solution of the time Schrödinger equation, the features of the excitation of a bound state of a particle in a one-dimensional rectangular quantum well of small depth by an extremely short light pulse are studied. The case of a shallow well with only one energy level is considered. In this case, the system is excited by an attosecond pulse whose duration is shorter than the characteristic time associated with the energy of the bound state of the particle in the well. It is shown that in this case the population of the bound state and the ionization probability are determined by the ratio of the electric area of the pulse to its atomic measure, which is inversely proportional to the well width. The calculation results showed that unipolar subcycle pulses with nonzero electric area can excite the system faster and more efficiently than bipolar pulses with zero area. The possibility of using unipolar gamma-ray pulses of zeptosecond duration for deuteron excitation is discussed, and numerical estimates of the required duration and electric area of the pulse are given.