Potential Quantum Wells Research Articles

Effects of hydrostatic pressure, aluminium composition, and external magnetic field on intersubband and intrasubband transitions characteristics in symmetric potential quantum wells

Aluminium composition (λ), magnetic field (B), and hydrostatic pressure (P) influences on magneto-optical (MO) properties of intra- and inter-subband transitions in GaAs/AlλGa1−λAs symmetric QWs for four models of confined optic phonons are studied and compared. The findings indicate: the MO characteristics of intra- and inter-subband transitions are significantly influenced by B, λ, and P for phonon absorption and emission. The e–p interaction intensity decreases as P increases, whereas it increases as λ increases. The influences of λ and P on phonon absorption are more significant than those on emission. E–p interaction intensity dependence on λ and P for intra-subband transitions is stronger than that for inter-subband ones. The e–p interaction in QWs is well described by Knipp–Reinecke and Huang–Zhu models. To reduce the influence of P on MO properties, we can increase T and λ or decrease B. At T≈600 K, the influence of P is insignificant and can be neglected.

Effect of the electronic confinement potential on the electron–LO-phonon interaction energy in a quantum well

We investigated the effect of the electronic confinement potential on the electron–LO-phonon (el–LO-ph) interaction energy in a quantum well by using the variational method. In this work, the el–LO-ph interaction energy in the infinite (I) and finite (F) square potential quantum wells (SPQW) is calculated as a function of the well-width for all four different confined-optical-phonon (COP) models. The result shows that the el-LO-ph interaction energy in a quantum well is affected strongly by the electronic confinement potential for all four COP models. Except for the Ridley-Babiker model, the el-LO-ph interaction energy in the ISPQW is always larger than that in the FSPQW for both the lowest phonon modes of different COP models in the narrow well case. The Fuchs-Kliewer and the Knipp-Reineck models have a good agreement in the description of the el-LO-ph interaction for the ISPQW, while that is the Fuchs-Kliewer and the Huang-Zhu models for the FSPQW. Among the above four models, the Fuchs-Kliewer model is the most effective.

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.

Cyclotron resonance in the Pöschl–Teller quantum well under the influence of the asymmetric parameters

In this article, a detailed study of the influence of the asymmetry parameter of the Pöschl–Teller potential quantum wells (PTPQW) on the cyclotron resonance absorption (CRA) power and the half-width or the full width at half maximum (FWHM) of the CRA-peak is reported utilizing the projection operator and profile methods, respectively. The main results of the research show that (i) the CRA-power in the PTPQW is affected strongly by the asymmetrical parameter λ; (ii) the FWHM of the CRA-peak in the PTPQW as functions of the PTPQW-width L, the magnetic field B, the electron concentration ne, the temperature T, and the Landau level n at several values of the asymmetrical parameter λ; (iii) the FWHM of the CRA-peak in the PTPQW always increases with the increasing asymmetrical parameter λ; (iv) the obtained results for the Pöschl–Teller QW are compared with those for the rectangular QW. (v) the PTPQW is a model which can yield promising magneto-optical properties, including the CRA-power and the FWHM of the CRA-peak for potential applications in the future to optoelectronic devices. The results of the present theoretical research are well consistent with those of the previous experimental one.

Asymmetrical Gaussian Potential Effects on Strongly Coupled Magnetopolaron Properties in Triangular Confinement Potential Quantum Wells

In this research, the existence of an asymmetrical Gaussian confinement potential (AGCP) along the quantum well (QW) growth direction and of a parabolic potential perpendicular to the polar coordinate direction were considered. The magnetic field and temperature properties of the longitudinal optical (LO)-phonon mean number, ground-state energy (GSE), ground-state binding energy (GSBE) and vibrational frequency (VF) of strongly coupled magnetopolarons in triangular confinement potential QWs (TCPQWs) were investigated according to the quantum statistical theory as well as the linear combination operator and unitary transformation methods. We obtained analytical expressions for the GSE, GSBE, VF and LO-phonon mean number as functions of the applied magnetic field, temperature, AGCP barrier height, AGCP range, polar coordinate system’s polar angle and polar coordinate system’s confinement strength. It was demonstrated by the calculated numerical results that the GSE, GSBE, VF and LO-phonon mean number varied with the related physical quantities. The obtained theoretical results are expected to provide a reference for future research on polarons.

The nonlinear optical rectification, second and third harmonic generation coefficients of Konwent potential quantum wells

The nonlinear optical rectification, second and third harmonic generation coefficients of Konwent potential quantum wells

Electromagnetic field effect on weak-coupling piezoelectric polaron in an asymmetrical Gaussian confinement potential quantum well

The properties of an electron weakly coupled to piezo-acoustic phonon in asymmetrical Gaussian confinement potential quantum well (AGCPQW) subject to external electric field (EF) and magnetic field (MF) has been investigated using the Lee-Low-Pines unitary transformation and linear combination operation methods. We have obtained the ground state energy (GSE) and the ground state binding energy (GSBE) of piezoelectric polaron. The effects of the EF, the MF, the range of the asymmetrical Gaussian confinement potential (RAGCP), Debye cut-off wavenumber (DCOW) and the electron–phonon coupling strength on the GSE and the GSBE are also analyzed. It is found that the GSE is an increasing function of the EF and the cyclotron frequency (CF), whereas it is a decreasing one of the RAGCP, the DCOW and electron–phonon coupling strength. The GSBE is an increasing function of the DCOW and the electron–phonon coupling strength. It is also an aggrandizing function with decreasing of the RAGCP, whereas it is a decayed one of the EF and CF. It is shown that the EF, the RAGCP, the MF, the DCOW and electron–phonon coupling strength are important factors that have great influence on the properties of the piezoelectric polaron in AGCPQW.

Gate-controlled proximity magnetoresistance in In1−xGaxAs/(Ga,Fe)Sb bilayer heterostructures

The magnetic proximity effect (MPE), ferromagnetic coupling at the interface of magnetically dissimilar layers, attracts much attention as a promising pathway for introducing ferromagnetism into a high-mobility non-magnetic conducting channel. Recently, our group found giant proximity magnetoresistance (PMR), which is caused by MPE at an interface between a non-magnetic semiconductor InAs quantum well (QW) layer and a ferromagnetic semiconductor (Ga,Fe)Sb layer. The MPE in the non-magnetic semiconductor can be modulated by applying a gate voltage and controlling the penetration of the electron wavefunction in the InAs QW into the neighboring insulating ferromagnetic (Ga,Fe)Sb layer. However, optimal conditions to obtain strong MPE at the InAs/(Ga,Fe)Sb interface have not been clarified. In this paper, we systematically investigate the PMR properties of In1-xGaxAs (x = 0%, 5%, 7.5%, and 10%) / (Ga,Fe)Sb bilayer semiconductor heterostructures under a wide range of gate voltage. The inclusion of Ga alters the electronic structures of the InAs thin film, in particular changing the effective mass and the QW potential of electron carriers. Our experimental results and theoretical analysis of the PMR in these In1-xGaxAs/(Ga,Fe)Sb heterostructures show that the MPE depends not only on the degree of penetration of the electron wavefunction into (Ga,Fe)Sb but also on the electron density. These findings help us to unveil the microscopic mechanism of MPE in semiconductor-based non-magnetic/ferromagnetic heterojunctions.

Asymmetrical semi-exponential potential effect of exciton in strong-coupling alkali halide quantum well

Within the framework of the method of Lee-Low-Pines unitary transformations and variations, strong-coupling exciton-longitudinal-optical (LO) phonon interaction in asymmetric semi-exponential potential quantum wells was investigated. It is shown that the self-trapping energy, effective potential and vibration frequency of the exciton, depends significantly on the parameters of the confined potential, electron-hole distance and electron-hole mass.

Influence of the confining potential on the linewidth of a quantum well

In this theoretical study, we consider in detail the influence of the confining potential on the magneto-optical absorption linewidth (MOALW) of a quantum well for both intersubband and intrasubband magneto-optical transitions. The projection operator method and the profile technique are used to calculate respectively the MO-absorption power and MOALW in both the semiparabolic, parabolic, and the rectangular confining potential quantum wells. The results obtained from the present study show that (i) the MOALW as functions of the structural, material, and external parameters include the confining potential frequency, the well width, the electron density, the temperature, and the magnetic field, as well as Landau level number; (ii) the larger contribution from intrasubband transitions to electron-phonon scattering compared with intersubband transitions for both three type of above confining potentials; (iii) the dependence of the MOALW on the above parameters is found to be the strongest in case of the square confining potential quantum well while it is the weakest in case of the semiparabolic confining potential quantum well for intersubband magneto-optical transitions, however, that for the parabolic confining potential is similar to the rectangular confining potential for intrasubband magneto-optical transitions. Our present calculations accord well with previous experimental studies. • Influence of the confining potential on the linewidth of a quantum well is studied in detail. • Linewidth is affected by confining frequency, temperature, magnetic field, electron density, well-width, and Landau level. • Intersubband transition linewidth is compared with intrasubband one in both three potential wells. • Linewidth in semiparabolic potential well is compared with that in rectangular and parabolic wells. • Quantum confining potential effects significantly on the linewidth of a quantum well.

The effect of parabolic potential on ground state energy and vibration frequency of magnetopolaron in asymmetric Gaussian potential quantum wells

Anisotropy parabolic potential (APP) effects on ground state (GS) energy [Formula: see text] and the vibration frequency (VF) [Formula: see text] of weak-coupled magnetopolaron (MP) in asymmetric Gaussian quantum wells (AGQWs) were investigated using the linear combination operator and unitary transformation method. The obtained results showed that [Formula: see text] and [Formula: see text] were increased by increasing the barrier height [Formula: see text] of AGQWs as well as transverse and longitudinal confined strengths [Formula: see text] and [Formula: see text] of APP and decreased with increase in the asymmetric Gaussian confinement potential (AGCP) range [Formula: see text] and transverse and longitudinal effective confined lengths [Formula: see text] and [Formula: see text] of APP. Thus, the GS energy and VF of MP could be changed by adjusting the confinement parameters of the APP and AGCP. The study of quantum wells’ semiconductor materials has broad potential applications in semiconductor lasers, optoelectronic devices and quantum information.

The influences of hydrogen-like impurities and magnetic field on magnetopolaron in asymmetric semi-exponential and parabolic potential quantum wells

In the current research, the impacts of anisotropic parabolic confinement potential (APCP) on strong-coupled impurity bound magnetopolaron (SCIMP) in asymmetrical semi-exponential quantum wells (ASEQWs) containing hydrogen-like impurities (HLIs) at their center under uniform magnetic fields applied along the direction of z axis have been theoretically investigated. Lee-Low-Pine unitary transformation and linear combination operation methods were applied for the derivation of formulations for ground state energy (GSE) and the mean number of LO phonons (MNLOP) of SCIMPs. Also, GSE and MNLOP as functions of magnetic field cyclotron frequency, Coulombic impurity potential (CIP) strength, APCP effective confinement strengths along x and y directions, and two positive parameters of asymmetrical semi-exponential confinement potential (ASECP) were acquired. Numerical results were expressed for a typical CsI. It was found that when considering magnetic field, APCP, CIP, ASECP, GSE and MNLOP were increased.

Comparison of the magneto-optical properties of the semi-parabolic well with those of the parabolic and rectangular wells under the combined influences of aluminum concentration and hydrostatic pressure

In this paper, we report the comparison of the magneto-optical transport properties of the semi-parabolic potential quantum well with those of the parabolic and rectangular potential quantum wells under the combined influences of the aluminum concentration, the temperature, the hydrostatic pressure, and the Landau levels by using the methods of the quantum field theory for many-particle systems in statistical physics and the profile to calculate analytically the conductivity tensor expression, the magneto-optical absorption power expression of the optically detected magneto-phonon resonance (ODMPR) oscillation, and the full width at half maximum (FWHM) of the ODMPR peak, respectively, in quantum wells with three above different confining potential shapes for typical GaAs/AlxGa1−xAs material. The results obtained from the present study show that (i) the ODMPR peak position undergoes a red-shift as the aluminum concentration and the hydrostatic pressure increase while it experiences a blue-shift as the temperature augments for all three above confining potential shapes; (ii) the FWHM as functions of the barrier's Al-concentration, the system's temperature, and the hydrostatic pressure for all three confining potential shapes is presented to compare; (iii) the dependence of the FWHM on the barrier's Al-concentration and the hydrostatic pressure for the Landau levels for three confining potential shapes also is taken into account in detail; (iv) our present theoretical calculations are found to be consistent with previous experimental calculations.

The temperature effect on ground state binding energy of a strong-coupling magnetopolaron in an asymmetrical Gaussian potential quantum well

This paper utilized the methods of linear combination and unitary transformation to evaluate the vibrational frequency (VF) and ground state binding energy (GSBE) of a strong-coupling magnetopolaron in an asymmetrical Gaussian potential quantum well (AGPQW), and the effects of the temperature on these physical quantities were studied through quantum statistical theory. The changes of the VF and GSBE versus temperature and cyclotron frequency (CF) in a magnetic field were discussed. The numerical calculations revealed that with the increase of temperature, the VF and GSBE also increased. Meanwhile, the numerical results show that the VF increases with the increase of the CF. However, the GSBE versus the CF has different changing properties.

The effect of temperature on strong-coupling magnetopolaron in an asymmetrical Gaussian potential quantum well

The influences of temperature and cyclotron frequency of a magnetic field on the ground state energy and mean number of phonons (MNP) of strong-coupling magnetopolarons in an asymmetric Gaussian potential quantum well(AGPQW) are researched by employing the linear-combination operator method and the unitary transformation. It was demonstrated through the numerical calculations that the ground state energy and the MNP increase with higher magnetic field cyclotron frequencies and temperature. In addition, increasing of the barrier of asymmetric Gaussian potential (AGP) causes the ground state energy to decrease while increasing the MNP of magnetopolarons.

Intense laser-induced electronic and optical properties in double finite oscillator potential

ABSTRACTIn the present paper, a theoretically study of the non-resonant laser field effect on the optical response, such as nonlinear optical rectification (NOR), second (SHG) and third harmonic generation (THG) coefficients in double finite oscillator potential (DFO) quantum wells is performed in the framework of the effective mass approximation. The obtained results reveal that, energy states and optical response is significantly affected by the non-resonant intense laser field (ILF) intensity and symmetry of the structure. Also it was found that the laser field is more effective on the optical response in the DFO potential when the asymmetric character of the confinement potential is strong. Thus, the NOR, SHG and THG coefficients with designated values can be obtained by using a properly adjusted ILF intensity and symmetry parameter of confinement potential.

Effect of applied external fields on the nonlinear optical properties of a Woods-Saxon potential quantum well

In this present work a detailed theoretical study on the influence of the static electric, magnetic, and non-resonant intense THz laser fields on the nonlinear optical properties such as nonlinear optical rectification (NOR) and second harmonic generation (SHG), of a quantum well that has the Woods-Saxon potential profile. The static electric and high-frequency intense THz laser fields are applied along the growth-direction of the structure whilst the static magnetic field is applied perpendicular to them. The outcome of the numerical calculation demonstrates that, both the peak potions of the NOR and SHG coefficients exhibit a blue-shift with the increment of the static electric and magnetic fields, but their peak amplitudes increases with the magnitude of the electric field whilst decreases with the magnitude of the magnetic field. However, the peak positions of the NOR and SHG coefficients exhibit firstly a blue-shift, and then a red-shift with the increment of the laser intensity, but their peak amplitudes increases. We hope that these theoretical results will be useful for designing new optoelectronic devices with a performance tailored by the adjustment of the applied fields.

Electron-related optical responses in Gaussian potential quantum wells: Role of intense laser field

A theoretical study of the effects of non-resonant intense laser field on the optical response in a Gaussian potential quantum well is performed in the framework of the effective mass approximation. The obtained results indicate that, the depth and range of the considered confinement potential and intense laser field intensity has a significant effect on the optical properties in Gaussian potential quantum wells. Also it was found that the laser field is more effective on the optical response in Gaussian potential quantum wells with smaller range.

The influences of electric field and temperature on state energies of a strong-coupling polaron in an asymmetric Gaussian potential quantum well

We investigate the electric field effect on the ground state (GS), the first-excited state (FES) and the excitation energies of a strong-coupled polaron in an asymmetric Gaussian potential (AGP) quantum well (QW) by using a variational method of the Pekar type (VMPT). By employing the quantum statistics theory (QST), we also study the temperature effects on the state energies (SE). It is found that the SE of polaron are an increasing function of temperature. The polaron's SE are decreasing functions of electric field, but the excitation energy is an increasing one.

Effect of temperature on the ground state of polaron in an asymmetrical Gaussian potential quantum well

The ground state energy (GSE), the ground state binding energy (GSBE) of the strong coupling polaron in the asymmetrical Gaussian potential quantum well (AGPQW) are received by using the linear combination operator and the second unitary transformation methods. Effects of temperature and the height and the range of the asymmetrical Gaussian potential (AGP) on these two physical quantities are performed and indicated that (i) the absolute value of GSE increases (decreases) when the temperature increases at lower (higher) regime and it's an increasing function of the height and the range of AGP, however, effect of the AGP's range on it is weaker at higher temperature regime; (ii) The GSBE will increase with the increase of the temperature, the height and the range of the AGP.