Parabolic Confinement Research Articles

Energy level spectrum and lattice polarization of polaron in metal halide perovskite parabolic quantum wells

In this study, polaron effect in 2D metal halide perovskite materials (TMHPMs), which naturally form quantum well (QW) structures, has been investigated. Polarization of carriers and lattice within these structures was explored based on unitary transformation and variational methods. Specifically, lattice polarization and energy level transition spectra of strong coupling polaron in parabolic potential metal halide perovskite QWs (MAPbCl3, MAPbBr3, and MAPbI3) were studied. Also, we calculated ground and first excited state energies, excitation energy, transition frequency, and vibration frequency of a TMHPM QWs. Our results indicated that parabolic potential confinement intensity affected related physical quantities, which provided insight to investigate metal halide perovskite materials and polaron effect.

Evidence of two-dimensional lateral quantum confinement in self-formed core–shell InGaN nanowires on Si (111) emitting in the red

The proof of strong two-dimensional lateral quantum confinement in the In-rich core of red-light emitting self-formed core–shell InGaN nanowires is given. The nanowires are directly grown on Si (111) by plasma-assisted molecular beam epitaxy. After the initial InGaN nucleation, straight nanowires with quantum-size core radius determined by x-ray diffraction, transmission electron microscopy, and energy dispersive x-ray mappings develop. Detailed comparison of the photoluminescence from the core, the In contents of the core and shell, and the core radius with theoretical modeling reveals a parabolic confinement potential with large ground state quantum confinement energies of electrons and holes. Such strong lateral quantum confinement in a vertical quantum wire active region is ideal for the performance of optoelectronic devices, in particular of our reported red InGaN light emitting diode with high brightness and color stability.

Biexcitons and quadrons in self-assembled quantum dots

We theoretically study biexcitons and quadrons in quantum dots with parabolic confinement and give a complete comparison between the two excitations. The calculation of quadron and biexciton binding energies as functions of electron-to-hole confinement potentials and mass ratios, using the unrestricted Hartree–Fock method, shows the essential differences between biexcitons and quadrons. The crossover between the negative and positive binding energies is indicated. The effect of an external magnetic field on the quadron and biexciton binding energies has also been investigated. In addition, the crossover between anti-binding and binding of both excited quadron and biexciton states in a certain range of the electron-to-hole oscillator length ratios has been found.

Energy spectrum and optical properties in a double parabolic quantum ring: Effects of the impurity, the magnetic field and the spin–orbit interaction

In this letter, the energy spectrum in a concentric double quantum rings(CDQRs) with a parabolic confinement under the influence of the spin–orbit interactions (SOIs), the magnetic field and the hydrogenic donor impurity has been investigated by diagonalizing the Hamiltonian matrix and applying the perturbation theory. Then the optical absorption coefficients (OACs) are calculated through the scheme of compact density-matrix formalism. A discussion of the different intensity of the two SOIs is conducted. Meanwhile, the effects of different factors on the total OACs with different incident light polarization angles have also been investigated, in which the bleaching effects are found.

O rassloenii monosloya zaryazhennykh mikrochastits v parabolicheskom uderzhivayushchem potentsiale

The evolution of an initially planar monolayer of charged microparticles in a complex plasma (plasma crystal) in horizontal (in the plane of the monolayer) and vertical parabolic confinements has been considered. The separation (buckling instability) of a Yukawa system into several layers at the weakening of the vertical confinement, as well as structural changes in such a plasma crystal, has been studied using the molecular dynamics method. In particular, it has been shown that the radial inhomogeneity of the plasma crystal qualitatively changes the character of the separation compared to homogeneous systems. Indeed, the separation begins in the center of the crystal, where the average distance between particles is minimal, and propagates in the form of a wave towards the periphery of the system at the weakening of the vertical confinement. This explains features of the behavior of plasma crystals in recent experiments with the complex plasma.

Amplitude modulation and surface wave generation in a complex plasma monolayer.

The response of a two-dimensional plasma crystal to an externally imposed initial perturbation has been explored using molecular dynamics (MD) simulations. A two-dimensional (2D) monolayer of micron-sized charged particles (dust) is formed in the plasma environment under certain conditions. The particles interacting via Yukawa pair potential are confined in the vertical (z[over ̂]) direction by an external parabolic confinement potential, which mimics the combined effect of gravity and the sheath electric field typically present in laboratory dusty plasma experiments. An external perturbation is introduced in the medium by displacing a small central region of particles in the vertical direction. The displaced particles start to oscillate in the vertical direction, and their dynamics get modulated through a parametric decay process generating beats. It has also been shown that the same motion is excited in the dynamics of unperturbed particles. A simple theoretical model is provided to understand the origin of the beat motions of particles. Additionally, in our simulations, concentric circular wavefronts propagating radially outward are observed on the surface of the monolayer. The physical mechanism and parametric dependence of the observed phenomena are discussed in detail. This research sheds light on the medium's ability to exhibit macroscopic softness, a pivotal characteristic of soft matter, while sustaining surface wave modes. Our findings are also relevant to other strongly coupled systems, such as colloids and classical one-component plasmas.

On the Separation of a Monolayer of Charged Microparticles in a Parabolic Confinement

On the Separation of a Monolayer of Charged Microparticles in a Parabolic Confinement

Caloric Effect Due to the Aharonov-Bohm Flux in an Antidot.

In this work, we report the caloric effect for an electronic system of the antidot type, modeled by combining a repulsive and attractive potential (parabolic confinement). In this system, we consider the action of a perpendicular external magnetic field and the possibility of having an Aharonov-Bohm flux (AB-flux) generated by a current passing through a solenoid placed inside the forbidden zone for the electron. The energy levels are obtained analytically, and the model is known as the Bogachek and Landman model. We propose to control the caloric response of the system by varying only the AB-flux, finding that, in the absence of an external magnetic field, the maximization of the effect always occurs at the same AB-flux intensity, independently of the temperature, while fixing the external magnetic field at a non-zero value breaks this symmetry and changes the point where the caloric phenomenon is maximized and is different depending on the temperature to which the process is carried. Our calculations indicate that using an effective electron mass of GaAs heterostructures and a trap intensity of the order of 2.896 meV, the modification of the AB-flux achieves a variation in temperature of the order of 1 K. Our analysis suggests that increasing the parabolic confinement twofold increases the effect threefold, while increasing the antidot size generates the reverse effect, i.e., a strong decrease in the caloric phenomenon under study. Due to the great diversity in technological applications that have antidots in electronics, the possibility of controlling their thermal response simply by varying the intensity of the internal current inside the solenoid (i.e., the intensity of AB-flux) can be a platform of interest for experimental studies.

Second-order adiabatic connection: The theory and application to two electrons in a parabolic confinement.

The adiabatic connection formalism, usually based on the first-order perturbation theory, has been generalized to an arbitrary order. The generalization stems from the observation that the formalism can be derived from a properly arranged Taylor expansion. The second-order theory is developed in detail and applied to the description of two electrons in a parabolic confinement (harmonium). A significant improvement relative to the first-order theory has been obtained.

Analytical formulation for exciton in semiconductor quantum dot with parabolic confinement

The exciton properties in cubical quantum dot (CQD), with parabolic confining potential, are theoretically investigated. We have used the two-band model, the effective mass approximation, and the variational method. The analytical expressions of the binding energy, the normalized photoluminescence (PL) energy transition, the spatial extension, and the oscillator strength of the exciton, in the ground state, have been obtained. The numerical calculations for the typical GaAs/Al x Ga1− x As CQD are presented. The effects of the CQD length and the Al concentration on the exciton properties are discussed. The results of the calculation illuminate that Al concentration and the CQD length can make an important impact on the exciton binding energy and the PL peak energy.

Inductively shunted transmons exhibit noise insensitive plasmon states and a fluxon decay exceeding 3 hours

Currently available quantum processors are dominated by noise, which severely limits their applicability and motivates the search for new physical qubit encodings. In this work, we introduce the inductively shunted transmon, a weakly flux-tunable superconducting qubit that offers charge offset protection for all levels and a 20-fold reduction in flux dispersion compared to the state-of-the-art resulting in a constant coherence over a full flux quantum. The parabolic confinement provided by the inductive shunt as well as the linearity of the geometric superinductor facilitates a high-power readout that resolves quantum jumps with a fidelity and QND-ness of >90% and without the need for a Josephson parametric amplifier. Moreover, the device reveals quantum tunneling physics between the two prepared fluxon ground states with a measured average decay time of up to 3.5 h. In the future, fast time-domain control of the transition matrix elements could offer a new path forward to also achieve full qubit control in the decay-protected fluxon basis.

Semi-analytical formulation for exciton in cuboidal semiconductor quantum dot with parabolic confinement: Hydrostatic pressure and temperature effects

The exciton properties in a cubical quantum dot (CQD), with parabolic confining potential, are theoretically investigated. We have used the two-band model, the effective mass approximation, and the variational method. An analytical formulation to be used for calculating exciton properties in a cubical quantum dot with a parabolic potential profile has been developed. The analytical expressions of the binding energy, the normalized photoluminescence energy transition, the spatial extension, and the oscillator strength of the exciton, in the ground state, have been obtained. The numerical calculations for the typical GaAs/AlxGa1−xAs CQD are presented. The effects of the side length of a cubic quantum dot, the hydrostatic pressure, and the temperature on the exciton properties are discussed. The results of the calculation illuminate that the hydrostatic pressure and the CQD length can make an important impact on the exciton binding energy and the photoluminescence peak energy.

On- and off-center helium atom in a spherical multilayer quantum dot with parabolic confinement

The ground state energy of a helium atom inside a spherical multilayer quantum dot as a function of the atomic impurity location inside the quantum dot has been calculated. The multilayer quantum dot is modeled by a core/shell/well/shell structure using a parabolic confinement. The Configuration Interaction method and the Diffusion Monte Carlo have been used to solve the Schrödinger equation. Results obtained showed that the lowest energy configuration depends on the size of the different layers of the quantum dot and agreement between Configuration Interaction and Diffusion Monte Carlo results indicates that the Configuration Interaction approach used here would be suitable to compute excited states of this system.Graphical abstract

Effect of number of well and core radius on the binding energy and optical properties of multishell spherical quantum dot with parabolic potential

In the current study, the probability densities and binding energy of the ground state and first excited sate in multishell quantum dot with parabolic confinement potential have been examined. Also, the effects of core radius, the number of well in structure and the presence of impurity on the total optical absorption coefficient have been investigated. The finite difference method has been used to obtain the energy levels and related wave functions of the system within framework effective mass approximation. The results obtained reveal that the number of well, especially the first five values, have a considerable impact on the critical core values of binding energy. It is found that the presence of impurity and the number of wells cause a blue shift in the peak positions of total absorption coefficients. Moreover, our results show that these factors have an important effect on the magnitude of optical properties.

Tailoring optoelectronic properties of InGaN-based quantum wells through electric field, indium content, and confinement shape: A theoretical investigation

This paper conducts a comprehensive theoretical examination of the electronic and optical responses, including linear and nonlinear optical responses, of an InGaN-based quantum well with a variable inverted parabolic confinement potential. This examination takes into account the effects of applied vertical electric fields, variable indium content, different confinement shapes, and sizes. The Schrödinger equation is solved numerically using the finite element method and the effective mass theory. The results indicate that both the electrical and optical properties of the system are highly influenced by these factors. Additionally, it is found that by carefully selecting these factors, the total optical absorption coefficient, total refractive index, and linear complex optical susceptibility of the system can be precisely controlled. This study makes a valuable theoretical contribution to the understanding of how electromagnetic radiation interacts with matter and can be applied to help explain the absorption and scattering properties of III-nitride materials, used in the active regions of various devices such as solar cells, photodetectors, and modulators, as well as in the design stages of them.

Polarization-dependent intervalence band absorption in quantum dots

In this work, we compute the electronic band structure of ZnCdSe/ZnS semiconductor quantum dots (QDs) using k. p method, and studied the dependence of QDs parameters on the in-plane polarization anisotropy and degree of polarization (DOP) of intersubband absorption spectra of QDs. Higher energy levels in the valence band show nonlinear dependence on the parabolic confinement strength and exhibit strong anti-crossing. We find that the optical transitions for specific polarization directions are defined by the size, strain, and shape anisotropy of the QDs. We observe that increasing the shape anisotropy, strain, and QDs radius enhanced the in-plane polarization anisotropy, whereas increasing QDs height reduces the in-plane polarization anisotropy. The DOP is found to increase with increasing QDs radius and strain and reducing the shape anisotropy and QDs height. Furthermore, the QDs parameters play a key role in deciding the absorption peak of the specific polarization. The present study suggests that the combination of shape, size, and strain could provide an optimal approach to tune the intraband polarization response from QDs.

Polaron level spectrum in double-potential quantum wells

The description of macroscopic systems of quasi-particles is a bright spot in quantum physics, providing an accurate description of the physics development. The current study presents a theoretical study of the energy level spectrum of weakly coupled polarons in polar crystals (GaAs, PbSe, PbTe) in double potential quantum wells (parabolic and asymmetric Gaussian confinement potentials) using the linear combination operator and two simple unitary transformations. Rigorous electron-phonon coupling interaction results are obtained under the weak coupling limitation. The results indicate that the polaron energy is relatively lower than that of the electron and the coupling strength affects the energy difference between polaron and electron. The influence of quantum wells’ confinement potential on energy is also discussed. These findings provide the possibility for potential application of polaron.

Impurity-related electronic properties in GaAs quantum disk under external excitations considering the confinement parabolicity effect

In this study, we investigated the ionization energy of the lowest bound-state donor-impurity in GaAs quantum disks under external electric and magnetic fields. We also examined its diamagnetic response, taking into account the parabolic confinement potential. Using the effective-mass approximation and Ritz's variational approach, we solved the Schrödinger equation. Our results demonstrate that both the electric and magnetic fields have a significant impact on the ionization energy and diamagnetic response. Additionally, the inclusion of the parabolic confinement potential changes the behavior of these properties. This study contributes to the understanding of the magneto-electrical properties of semiconductor quantum dots under external excitations and builds on our prior work on this topic.

The Study of the Spectral Properties of a Spatially Inhomogeneous System of Yukawa Particles in a Parabolic Confinement

The Study of the Spectral Properties of a Spatially Inhomogeneous System of Yukawa Particles in a Parabolic Confinement

Effect of hydrostatic pressure and temperature on the ballistic conductance under the influence of Rashba spin-orbit coupling

In semiconductors, the exploration of electron quantum transport on the nanoscale has become feasible due to the electric field as well as magnetic field impact. The existence of spin-orbit coupling in the quantum wire has set up a propitious stage for the development of apparatus for electron transportation. Here, we analyse the impact of hydrostatic pressure and temperature on the energy band structure as well as on the ballistic conductivity. The Energy eigenvalues and eigenvectors are found by using the diagonalization method and the ballistic conductance is computed by Landuer-B u¨ ttiker formalism. Also, we have studied the behaviour of energy concerning an external electric field, magnetic field and temperature. The system is expressed by parabolic confinement to the normal intense magnetic field and RSOI causes the collaborative impact of interior and exterior agents leading to downward/upward and lateral/vertical shifts in the dispersion. The oddity of the energy subbands results in oscillatory patterns in the ballistic conductance.