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In this work, we study cyclic codes of length n over a finite commutative non-chain ring ℛ = F q [ u , v ] / 〈 u 2 − γ u , v 2 − ϵ v , u v − v u 〉 where γ , ϵ ∈ F q * and we find new and better quantum error-correcting codes than previously known quantum error correcting codes. Then certain constraints are imposed on the generator polynomials of cyclic codes, so these codes become linear complementary dual codes (in short LCD codes). We then verify that the Gray image of linear complementary dual codes of length n over ℛ is a linear complementary dual code of length 4 n over F q by establishing a Gray map. [ABSTRACT FROM AUTHOR]

Electronic properties of a neutral donor confined in a GaAs coupled quantum dot-ring covered by a Al 0. 3 Ga 0. 7 As matrix were calculated using the finite element method under the effective mass and the envelope function approximations. The proposed model is set up to fit a realistic coupled quantum dot-ring geometry revealed by atomic force microscopy images. The results show that the energy levels and the transition energies in the presence of an electric field strongly depend on the donor center's angular position. Furthermore, the total optical absorption coefficient is calculated within the two-level approximation and the matrix density formalism. The absorption spectrum shows that the system can be tuned between 5 and 30 meV. Also, an optical transparency effect for different configurations characterized by specific donor center's angular positions and electric field values is seen. Finally, a novel redshift is observed when the sample temperature increases. • Donor states in coupled quantum dot-rings are calculated. • Energy levels and transition energies depend on the donor center's angular position. • System's absorption spectrum can be tuned between 5 and 30 meV. • Optical transparency effect seen for specific donor positions and electric fields. • A novel redshift is observed as the sample temperature increases. [ABSTRACT FROM AUTHOR]

A systematic study was undertaken to analyze the electronic and thermal properties of a single electron within a superelliptic quantum ring under orthogonal magnetic and electric fields. The corresponding Schrödinger equation for this system was numerically solved using the finite element method within the effective mass approximation. The influence of geometric effects associated with the morphology of the inner and outer contours of the superellipse, as well as the impact of external fields on electronic and thermal properties, were analyzed. The flexibility of the superellipse shape parameters considered in this study allows the consideration of different types of rings and the derivation of several electronic properties previously published in the literature as particular cases of our model. It was observed that thermal properties are highly sensitive to external fields and the geometrical potential linked to the topological variations experienced by the superellipse during the growth of the quantum rings. • Superelliptic quantum rings. • Entropy, heat capacity, internal energy, and Helmholtz free energy of single electron in Superelliptic quantum rings. • Electric and magnetic field effects on a of single electron in Superelliptic quantum rings. • Geometrical effects on a single electron in Superelliptic quantum rings. [ABSTRACT FROM AUTHOR]

The electronic and optical properties of an electron in realistic rectangle-shaped crater quantum rings under orthogonal electric and magnetic fields have been theoretically studied. The Schrödinger wave equation was solved using the finite element method within the effective mass approximation. A Stark effect with anomalous oscillatory behavior was observed for electric field strengths less than 10 kV/cm. The threading magnetic field leads to the formation of damped oscillations in the absorption coefficient peaks, which are closely related both to the Aharonov-Bohm oscillations and to a shift of the absorption peaks towards blue or red, depending on the dimensions and morphology of the central crater. Our model is sufficiently flexible such that several results appear as particular cases of the quantum ring with a rectangular central crater. • Rectangle-shaped crater quantum rings. • The energy structure of a single electron in a quantum ring with rectangle-shaped central crater. • Electric and magnetic field effects on a single electron in a quantum ring with rectangle shape central crater. • Optical response of an electron in quantum ring with rectangle-shaped crater under orthogonal electro-magnetic fields. [ABSTRACT FROM AUTHOR]

Microring resonators are pivotal in photonic and quantum technologies. Enhancing their versatility for various applications often involves integrating additional elements to modify their resonant lineshapes. In this regard, Nested Ring Resonators (NRRs) offer a novel approach to generate a variety of lineshapes without the need for supplementary components. The coupled resonant architecture of NRRs can induce phenomena such as Electromagnetically Induced Absorption, Electromagnetically Induced Transparency, Fano resonance, and double Fano resonance. This study comprehensively analyzes the different resonant lineshapes achievable with NRRs, highlighting their broad applicability. We identify the specific conditions required for each resonant phenomenon and closely examine their characteristics. The theoretical insights from our research enable the autonomous design and realization of various resonance lineshapes within an NRR, eliminating the need for additional components while maintaining device compactness for a wide range of practical applications. [ABSTRACT FROM AUTHOR]

We carry out a study on the validity and limitations of truncation schemes customarily employed to treat the quantum kinetic equations of motion of complex interacting systems. Our system of choice is a semiconductor quantum ring with one electron interacting with few magnetic impurities via a Kondo-like Hamiltonian. This system is an interesting prototype which displays the necessary complexity when suitably scaled (large number of magnetic impurities) but can also be solved exactly when few impurities are present. The complexity in this system comes from the indirect electron-mediated impurity–impurity interaction and is reflected in the Heisenberg equations of motion, which form an infinite hierarchy. For the cases of two and three magnetic impurities, we solve for the quantum dynamics of our system both exactly and following a truncation scheme developed for diluted magnetic semiconductors in the bulk. We find an excellent agreement between the two approaches when physical observables like the impurities' spin angular momentum are computed for times that well exceed the time window of validity of perturbation theory. On the other hand, we find that within time ranges of physical interest, the truncation scheme introduces negative populations which represents a serious methodological drawback. • Quantum dynamics of a DMS quantum ring. • Theoretical study of the dynamics of spin and orbital angular momentum. • Test of the formalism of equations of motion of density matrices. [ABSTRACT FROM AUTHOR]

We study the quantum dynamics of an electron subject to the Dresselhaus spin–orbit interaction (SOI) and few magnetic impurities confined in a narrow semiconductor quantum ring. The exchange interaction between the electron and the magnetic Mn impurities is modeled via a Kondo-like Hamiltonian. The role of the Dresselhaus SOI is to mediate between the orbital and spin angular momentum of the electron. Our goal is to explore and analyze in the time domain the transference of angular momentum between the electron and the system of Mn impurities. We aim to contribute to the search for mechanisms that facilitate the effective magnetization of the impurity system via the interaction with charge carriers, without the use of external magnetic fields. We pose and numerically solve the equations of motion of the reduced density matrix for our multiparticle system, resorting to a state-of-the-art truncation scheme. We first obtain the dynamics without the SOI and show how the Mn impurities strongly modify the electronic angular momentum. Secondly, we add the SOI and describe the competition that occurs between the two interaction mechanisms. In our analysis, we profit from the fact that for a one-dimensional quantum ring with only SOI the Hamiltonian reduces to block-diagonal form and the exchange interaction couples rather weakly different blocks. As general trends, we find that the SOI slows down the magnetization of the impurities and superimposes rapid oscillations in the evolution of the electron's orbital angular momentum. • Electron and Mn impurity angular momentum dynamics in DMS QR with Dresselhaus SOI. • Case study of a (Zn,Mn)Se DMS quantum ring in the highly-diluted limit. • Time-domain numerical study employing truncated density matrices. [ABSTRACT FROM AUTHOR]

This research investigates the influence of electric field orientation on the physical properties of a Gallium Arsenide (GaAs) Circular Toroidal Quantum Ring (CTQR) in the presence of shallow donor impurity. Using the effective mass approximation and an infinite potential well, we delve into how electric field directions specifically 0, 45, and 90 degrees on the xy-plane affect physical behaviors such as binding energy, electronic energy, the Stark effect, dipole moment and donor impurity position. Utilizing the finite difference method for our numerical analysis, we discovered interesting size-dependent behaviors. Our findings reveal intriguing insights. Initially, we observed that the electronic energy exhibits minimal sensitivity to the direction of the electric field in smaller CTQR. Notably, the ground state energy increases when the electric field's direction shifts from φ F = 0 to φ F = 9 0 ∘ . The electric field's influence on the binding energy varies depending on its orientation. In larger structures, we observe a lower binding energy. Thus, our study unveils the influence of the electric field's direction on Stark shifts and dipole moment which opens pathways for a deeper understanding of potential applications in this domain. • Applied external electric field on Circular Toroidal Quantum Ring. • The presence of the shallow donor atom has been considered. • Schrödinger equation of nanostructure has been solved by using 3D finite difference method. • Electric field orientation effect on Stark shift, dipole moment and binding energy. • The impact of the geometric and the size of nanostructure on the electronic spectrum. [ABSTRACT FROM AUTHOR]

In this work, we have examined the electronic and optical properties of three Variant Toroidal Quantum Ring (VTQR) materials, GaN, GaAs, and CdSe, in the presence of an axial magnetic field. Using an infinite potential model and based on the effective mass approximation, we calculated eigenvalues and eigenvectors using the three-dimensional finite difference method. This research aims to improve our understanding of the impact of the magnetic field on VTQRs of different sizes fabricated from various materials, such as GaAs, GaN, and CdSe. We simultaneously studied the geometrical parameters of VTQR nanostructures and the influence of the axial magnetic field on electronic energy, donor energy, electron-donor binding energy, magnetic shift, diamagnetic susceptibility, bandgap energy, and optical band gab. Our results show a strong correlation between electron-impurity binding energy, geometric parameters, and the presence of a magnetic field. CdSe consistently displays the highest binding energy, indicating superior stability under the study conditions. The effects of the magnetic field on these materials vary, with CdSe exhibiting increased sensitivity and GaAs demonstrating the lowest sensitivity. Nanostructure dimensions, including radii and curvature angles, play a central role in modulating the effects of binding energy and magnetic field, reflecting distinct electronic properties. • Electronic and optical properties of three different materials (GaN, GaAs and CdSe) have been focused. • Solving the Schrödinger equation by using three-dimensional finite difference method. • How Variant Toroidal Quantum Rings structures made from GaAs, GaN, and CdSe react with magnetic fields. • How geometric parameters like radii and curvature angles influence electronic properties under magnetic fields. [ABSTRACT FROM AUTHOR]

Within the framework of effective mass approximation and with the use of finite element method, we calculate the energy states of an electron in a double toroidal quantum ring with a Hopf link structure. The study includes the influence of externally applied static electric and magnetic fields, and considers different geometric combinations of radii and link positions. We have found that geometric manipulations have significant impact on the energy values and the distribution of electronic probability densities in either one or both linked rings. Similar effects can be achieved with the application of the electromagnetic probes. • Novel Hopf link quantum ring system has been modeled in finite potential barriers. • Electrical and magnetic fields tune the density probability of one confined electron. • Some geometric configurations allow overcoming the isolation of potential barriers. • Energy oscillations under magnetic field are only evident for excited states. [ABSTRACT FROM AUTHOR]

In this study, we explored the complex effects of electric fields in three unique directions and axial magnetic field on a GaAs-Variant Quantum Ring Quarter Cross-Section (VQRQCS), particularly when there is an off-center shallow donor impurity. The investigation explores the impact of these fields on various physical attributes, including electronic energy, binding energy, magnetic shift, Stark shift, average electron impurity distance, and diamagnetic susceptibility. Using effective mass approximation and three-dimensional finite difference methods we solved the Schrodinger equation. Our result shows that the geometric radius of the VQRQCS has an essential impact on electronic energy. Notably, as the radius increases, the electronic energy decreases, regardless of the presence of fields. In particular, we found that magnetic fields amplify the electronic energy of the ground state. The angle of curvature of the nanostructure and the direction of the electric field also play an important role. Additionally, the electron–impurity binding energy decreases with the growth of the nanostructure, with external fields intensifying this effect. The average distance between the electron and the impurity, analyzed in the context of simultaneously applied fields, provides insight into the Coulomb interaction. Diamagnetic susceptibility, measuring the response of a material to an external magnetic field, is studied, indicating opposition to the external field. In summary, this research highlights the nuanced interactions between electric and magnetic fields that determine the properties of a GaAs quantum ring, providing critical insights for quantum ring-based technological advancements. • Exploration of the intricate effects of electric fields in three unique directions and an axial magnetic field on a quantum ring nanostructure. • Electronic properties, magnetic shift, Stark shift, average electron–impurity distance, and diamagnetic susceptibility have been studied. • Discovery that the geometrical parameters of the quantum ring significantly influence the electronic energy. • The angle of curvature of the nanostructure and the direction of the electric field are found to be crucial factors. • Diamagnetic Susceptibility: Examination of how the material responds to an external magnetic field. [ABSTRACT FROM AUTHOR]

In this paper, we study the electromagnetically induced transparency (EIT) of a quantum ring by considering both interband and intraband transitions, under the influence of external electric and magnetic fields, as well as Rashba spin–orbit interaction (RSOI). Four band k ⋅ p model along with effective mass one band approximation were respectively employed to compute valence and conduction bands energy eigenvalues. We investigate the effects of applied electric and magnetic fields, as well as RSOI and the ring dimensions, on EIT. Our results reveal that the external magnetic field and the ring dimensions have a great influence on the EIT phenomenon. Ultimately, our numerical results will be used to develop devices with controllable nonlinear optical absorption and refraction. • Kohn-Luttinger Hamiltonian for holes is derived within the cylindrical coordinates. • Fields effect as well as RSOI on interband EIT in a QR are investigated. • Magnetic field has a great influence on EIT and the transparency window. • The ring size considerably changes the transparency window. [ABSTRACT FROM AUTHOR]

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. • The optical properties of a doped double parabolic concentric quantum rings. • Consideration of the effect of spin–orbit interactions. • Discussions on the behavior of different polarized incident light. • Optimization of the previous computation to gain properties of more complex systems. [ABSTRACT FROM AUTHOR]

In this study, we have investigated the combined influence of hydrostatic pressure and temperature on the electronic and optical properties of an electron and a off-center atom confined in a Hemi Quantum Ring. To analyze the system, we employed the finite difference method, considering the effective mass approximation and an infinite confinement potential. Our study examines the permanent dipole moment and diamagnetic susceptibility under the influence of the donor atom's position, temperature, and applied hydrostatic pressure in the three directions R g , R c and φ 0. Our results reveal that the permanent dipole moment increases as the geometric confinement decreases, while the diamagnetic susceptibility exhibits a negative behavior and is influenced by temperature and hydrostatic pressure. Furthermore, we observed that the bandgap and the optical bandgap are sensitive to variations in temperature and the size of the HQR (Hemi Quantum Ring) nanostructure. The study on the combined influence of hydrostatic pressure and temperature on the electronic and optical properties of an electron and an off-center atom confined in a Hemi Quantum Ring has potential real-world applications in the development of electronic and optical devices. • Electronic and optical properties of confined electron and an off-center atom in quantum ring. • Combined effects of hydrostatic pressure and temperature are examined. • Finite difference method is employed within the effective mass approximation. • Permanent dipole moment, diamagnetic susceptibility and optical bandgap are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically studied the interband transitions in a three-dimensional structure of GaAs/Al 0.3 Ga 0.7 As triple concentric quantum rings approximating a reported experimental case. An intense non-resonant laser field and/or a static electric field were appropriately chosen to investigate the heavy-hole spectra and the interband transitions. For the combined actions of the two fields acting in the horizontal plane of the structure, we considered parallel and perpendicular directions. In each study, the effects on the heavy-hole energy spectra were discussed concerning their relationship with wave function localization. The radiative recombination energies, overlap integrals, and interband transition lifetime emphasize regions of interest for efficient control of the radiative decay, which is important for practical applications. • We study interband transition in triple quantum ring in laser and electric fields. • We performed 3D numerical computation for energy spectra and wave functions. • Recombination energy decreases in electric field and increases with laser field. • Transition lifetime can be efficiently tuned by fields values and orientation. [ABSTRACT FROM AUTHOR]

A systematic study of the thermal properties of an artificial molecule formed by a single electron embedded in two laterally coupled quantum rings under external probes: magnetic and static electric fields was carried out. The eigen-states and eigen-values of the Hamiltonian in the effective mass approximation were obtained numerically. By varying the distance between the centers of the rings, it was possible to establish the equilibrium length required by the formation of a giant stable artificial molecular complex and its dissociation energy. These features were corroborated by studying the effects of the distance between centers of the rings, the magnetic and electric field on the entropy and heat capacity of the system. At low temperatures, the equilibrium condition of the artificial molecule is linked to the formation of a minimum value of the entropy and a peak in the heat capacity. The temperature's rising modifies substantially these conditions. • Artificial molecule quantum rings. • Entropy and heat capacity of two laterally coupled quantum rings. • Electric and magnetic field effects on artificial molecule thermal properties. • Geometrical effects on artificial molecule thermal properties. [ABSTRACT FROM AUTHOR]

We study a 2D mesoscopic ring with an anisotropic effective mass considering surface quantum confinement effects. Consider that the ring is defined on the surface of a cone, which can be controlled topologically and mapped to the 2D ring in flat space. We demonstrate through numerical analysis that the electronic properties, the magnetization, and the persistent current undergo significant changes due to quantum confinement and non-isotropic mass. We investigate these changes in the direct band gap semiconductors SiC, ZnO, GaN, and AlN. There is a plus (or minus) shift in the energy sub-bands for different values of curvature parameter and anisotropy. Manifestations of this nature are also seen in the Fermi energy profile as a function of the magnetic field and in the ring width as a function of the curvature parameter. Aharonov–Bohm (AB) and de Haas van-Alphen (dHvA) oscillations are also studied, and we find that they are sensitive to variations in curvature and anisotropy. • Surface geometric properties. • Direct band gap semiconductors. • Surface quantum confinement effects. • Two-dimensional mesoscopic ring. [ABSTRACT FROM AUTHOR]

A series of four novel BF 2 complexes of N -acetyl 2-aminobenzothiazoles featuring rigid rotorless polyheteroaromatic structures have been designed and synthesized. All of these compounds exhibited AIE properties with excellent solid-state fluorescence quantum yields up to 81.7%. Theoretical calculations revealed the characteristics of their ground-state structures and excitation processes. Their seemingly abnormal nonradiative decay in solutions was investigated from both direct vibrational relaxation and S 0 /S 1 surface crossing perspectives by the two-channel model. The minimum energy conical intersection (MECI) located by SF-TDDFT method indicated that the CI is mainly induced by the deformation of the BF 2 complex ring, leads to elevated energy level, and thus is not responsible for the fluorescence quenching. The potential energy curve (PEC) constructed along the distortion angle θ of BF 2 complex ring showed that when θ reaches 50° (the dark-state region approaching MECI), the energy barrier is only 0.11 eV, suggesting that the deformed dark state could serve as an effective deactivation channel via ultrafast internal conversion (IC). Crystallographic analysis illustrated that the F atoms perpendicular to the polyheterocycle could effectively prohibit detrimental π-π stacking and enhance intermolecular interactions, thereby resulting in efficient solid-state emission. [Display omitted] • Four BF 2 complexes of N -acetyl 2-aminobenzothiazoles were identified as AIEgens. • Deformation-induced MECI is not responsible for their nonradiative decay. • Accessible dark-state region upon deformation causes fluorescence quenching. [ABSTRACT FROM AUTHOR]

[Display omitted] • p -Hydroxyazobenzocrowns have been characterized with spectroscopic methods. • For the first time quantum yields values for p -hydroxybenzocrowns are given. • Fluorescence properties are dependent on macrocycle size. • Substituents in benzene rings affect the quantum yield values. The spectroscopic properties of a series of para -hydroxyazobenzocrowns, including three novel compounds, were investigated using UV–Vis absorption and emission spectroscopy. This study presents, for the first time, determined quantum yield (QY) values for macrocycles of this category, ranging between 0.122 and 0.195. The highest values were obtained for crowns bearing two phenyl substituents in benzene rings. The impact of aromatic ring substituents and macroring size on the spectral characterization (1H NMR and FTIR) of p -hydroxyazobenzocrowns was examined in consideration of the azophenol ⇄ quinone-hydrazone tautomeric equilibrium. Dipole moments of p -hydroxyazobenzocrowns in the ground and excited states have been determined. The alignment between experimental findings and theoretical studies was established. [ABSTRACT FROM AUTHOR]

Magnetic tuning of the bound exciton states and corresponding giant Zeeman splitting (GZS) between σ + and σ − excitonic transitions in CdTe/Cd 1-x Mn x Te quantum ring has been investigated in the Faraday configuration for various concentrations of Mn 2 + ions, using the variational technique in the effective mass approximation. The sp-d exchange interaction between the localized magnetic impurity ions and the delocalized charge carriers has been accounted via mean-field theory with the inclusion of a modified Brillouin function. The enhancement of the GZS, and in turn, the effective g-factor with the application of an external magnetic field, is strikingly manifested in type-I – type-II transition in the band structure, which has been well explained by computing the overlap integral between the electron and hole, and the in-plane exciton radius. This highlights the extraordinary magneto-optical properties, including the giant Faraday rotation and associated Verdet constant, which have been calculated using single oscillator model. The oscillator strength has been estimated, and is found to be larger than in the bulk diluted magnetic semiconductors (DMS) and quantum wells, reflecting stronger confinement inside the quantum ring. More extensive Zeeman splitting and a higher oscillator strength in the DMS-based QR lead to an ultra-high Verdet constant of 2. 6 × 1 0 9 rad/Tesla m , which are a few orders of magnitude larger than in the existing quantum systems and magneto-optical materials. [ABSTRACT FROM AUTHOR]

A ring resonator involves a scattering process where a part of the output is fed again into the input. The same formal structure is encountered in the problem of time travel in a neighborhood of a closed timelike curve (CTC). We know how to describe quantum optics of ring resonators, and the resulting description agrees with experiment. We can apply the same formal strategy to any looped quantum evolution, in particular to the time travel. The argument is in its essence a topological one and thus does not refer to any concrete geometry. It is shown that the resulting paradigm automatically removes logical inconsistencies associated with chronology protection, provided all input-output relations are given by unitary maps. Examples of elementary loops and a two-loop time machine illustrate the construction. In order to apply the formalism to quantum computation one has to describe multi-qubit systems interacting via CTC-based quantum gates. This is achieved by second quantization of loops. An example of a multiparticle system, with oscillators interacting via a time machine, is explicitly calculated. However, the resulting treatment of CTCs is not equivalent to the one proposed by Deutsch in his classic paper [1]. • Quantum time travel is an example of a looped quantum evolution. • Optical ring resonators are also examples of quantum looped evolutions – their description agrees with experiment. • The two cases can be treated as particular cases of the same abstract construction. • The resulting description of time travel removes paradoxes plaguing the more standard formulations. [ABSTRACT FROM AUTHOR]

Abstract The simultaneous effect of intense THz laser field and hydrogenic donor impurity on Aharonov-Bohm effect in a GaAs∕Ga 1− x Al x As single quantum ring is investigated using the non-perturbative Floquet theory in high-frequency limit and Ehlotzky approximation. It is shown that the intense THz laser field and donor impurity destroy the usual Aharonov-Bohm oscillations of the electron ground state. The Aharonov-Bohm-like oscillations of the excited energy levels, as well as the dipole, allowed optical transition energies can be effectively controlled by changing the laser field parameter and impurity position. Furthermore, an unusual oscillatory behavior is also observed for the dependence of optical transition intensity on magnetic field induction. The obtained results indicate the possibility of the prediction and effective control of electronic and optical properties of future devices on quantum rings. Highlights • Quantum Rings. • Intense laser field. • Impurity. • Magnetic field. • Intraband optical absorption. [ABSTRACT FROM AUTHOR]

Abstract The energy spectrum, dipole momentum, and polarizability induced by an off-axis donor in InAs/GaAs elongated volcano-shaped quantum dot in the presence of external electric and magnetic fields are theoretically investigated. Our calculations, carried out by using the adiabatic approximation and the Kane model, which takes into account the effect of non-parabolicity of the conduction band, show that estimated donor energies are essentially lower than corresponding values obtained by means of the effective mass approximation. The mixing of the donor's energies, the variation of the dipole moment, the electric polarizability and the charge distribution induced by the electric and magnetic fields are consistently described with our simple formalism, in which the adiabatic potential is related directly to the morphology of the elongated quantum ring. In this structure, the charge density in two lowest "bonding" and "anti-bonding" states tends to align along of one of two symmetry axes. The donor-electron Coulomb attraction leads to an increase of the energy gap between these states and provides a strong polarization of the anti-bonding state. The out-of-plane magnetic field decreases the overlapping of the corresponding wave functions, while the in-plane electric field increases their mixing and provides the reordering of the energy levels. We have found that the dependency of the polarizability on the external electric field in these conditions displays a phase transition to a donor state with a giant dipole moment. Highlights • Off-axis donor energy spectrum in elongated volcano-shaped quantum dot under electric and magnetic fields. • The charge density in "bonding" and "anti-bonding" states are aligned along of symmetry axes under external fields. • Electrical instability in the off-axis donor energy states is observed under orthogonal electric and magnetic fields. • Abrupt transition of the ground state to a giant dipole momentum configuration under growing electric field is observed. [ABSTRACT FROM AUTHOR]

Highlights • The dimensionality of coupled quantum rings was investigated in terms of the radiative decay time as a function of temperature. • Time-integrated photoluminescence intensity spectra were measured at various temperatures with a spectral redshift in coupled quantum rings. • The two dimensional density of states was obtained in terms of the power order (α = 1.0) from temperature-dependent radiative decay times. Abstract This study examined the temperature-dependent, time-integrated/-resolved photoluminescence of the exciton states in double GaAs quantum rings. The density of states was analyzed from the temperature-dependent radiative decay time of exciton states to better understand the intra-relaxation process from thermally excited exciton states. To distinguish the radiative decay time from a non-radiative process, the decay time from the exciton states was calibrated by a comparison with the photoluminescence intensity at low temperatures, where the non-radiative process can be negligible. In ideal quantum ring structures, the ring width becomes almost zero. Therefore, one-dimensional nature would be expected. On the other hand, this assumption is not valid because widthless ring structures cannot be grown using current growth techniques. In other words, the quasi-one-dimensional nature (power order of the temperature dependence from radiative decay times ∼0.8 between 1.0 (two-dimensional nature) and 0.5 (one-dimensional nature)) was observed in quantum ring structures when the ring width was comparable to the radius of the ring structures. In the case of double quantum rings, however, the power order of the temperature dependence was obtained from the radiative decay times, which gave rise to 1.0, corresponding to a two-dimensional nature. This increased dimensional nature can be attributed to the appreciable ring width and ring size, extended wave function due to optical coupling, and the presence of dark exciton states. [ABSTRACT FROM AUTHOR]

The combined influence of externally applied magnetic and non-resonant intense laser fields (ILF) on the electronic states of GaAs-based two-dimensional circular quantum rings is investigated. The behavior of the electron energy levels as a result of the variation in the strength of the external fields is studied. In particular, the effects of changing the polarization of the intense laser radiation on the conduction band potential profile and allowed energy levels are discussed in detail. The intraband transition energies and the dipole matrix elements are analyzed as functions of the applied magnetic field intensity for different combinations of the intense laser field and resonant probe laser radiation polarizations. The findings can be summarized as follows: i) the quantized energies steadily increase as functions of the magnetic field and ILF-effects, ii) the electric dipole matrix elements are larger for the case of circular non-resonant ILF-polarization and circular laser probe polarization with respect to the case of linear polarized radiation, and iii) the dipole matrix elements have oscillatory behavior due to the complex nature of the wave functions which stems from the imaginary term appearing in the Hamiltonian when magnetic field effects are included. • Combined effects of magnetic and non-resonant intense laser fields. • GaAs-based two-dimensional circular quantum rings. • Effects of the intense laser radiation polarization. • Intraband transition energies and absorption amplitudes are analyzed. • Optical Aharonov-Bohm oscillations are observed for the absorption. [ABSTRACT FROM AUTHOR]

Abstract Shannon quantum information entropies S ρ , γ , Fisher informations I ρ , γ , Onicescu energies O ρ , γ and complexities e S O are calculated both in the position (subscript ρ) and momentum (γ) spaces for the azimuthally symmetric two-dimensional nanoring that is placed into the combination of the transverse uniform magnetic field B and the Aharonov–Bohm (AB) flux ϕ A B and whose potential profile is modelled by the superposition of the quadratic and inverse quadratic dependencies on the radius r. The increasing intensity B flattens momentum waveforms Φ n m (k) and in the limit of the infinitely large fields they turn to zero: Φ n m (k) → 0 at B → ∞ , what means that the position wave functions Ψ n m (r) , which are their Fourier counterparts, tend in this limit to the δ -functions. Position (momentum) Shannon entropy depends on the field B as a negative (positive) logarithm of ω e f f ≡ (ω 0 2 + ω c 2 / 4) 1 / 2 , where ω 0 determines the quadratic steepness of the confining potential and ω c is a cyclotron frequency. This makes the sum S ρ n m + S γ n m a field-independent quantity that increases with the principal n and azimuthal m quantum numbers and does satisfy entropic uncertainty relation. Position Fisher information does not depend on m , linearly increases with n and varies as ω e f f whereas its n and m dependent Onicescu counterpart O ρ n m changes as ω e f f − 1. The products I ρ n m I γ n m and O ρ n m O γ n m are B -independent quantities. A dependence of the measures on the ring geometry is discussed. It is argued that a variation of the position Shannon entropy or Onicescu energy with the AB field uniquely determines an associated persistent current as a function of ϕ A B at B = 0. An inverse statement is correct too. Highlights • Uniform magnetic field can not alter a sum of the position and momentum Shannon information entropies of the quantum ring. • Products of the position and momentum Fisher informations and Onicescu energies are field-independent quantities too. • Position Shannon information entropy dependence on the Aharonov–Bohm flux mimics that of the energy spectrum. [ABSTRACT FROM AUTHOR]

Abstract We consider the single- and two-electron systems confined in concentric double quantum ring (DQR) nanostructure which interacts with transient perpendicular magnetic field oscillating with THz frequency. For this purpose we find the solutions of time-dependent Schrödinger equation utilizing Configuration Interaction method. We found that the transient magnetic field mixes the radial states, what trigger off the charge density oscillations in this direction, and these may be accompanied by spin oscillations, provided that a spin-orbit interaction (SOI) is involved. The pattern of density oscillations is more regular than those obtained for single- and two-electron spins what results from less complicated excitation energy spectra if SOI is not present in the system. The latter can be made more regular, i.e. the fluctuations of frequency and amplitude of spin oscillations shall be smaller, provided that the sign of the magnetic field at the beginning of time evolution is chosen appropriately since not all energy levels corresponding to J ˆ z − = L ˆ z − S ˆ z eigenstates have mirror symmetry in relation to B → − B transformation. Our outcomes indicate, that the combined effect of a few-picosecond-long magnetic pulse and SOI on electron spin in DQR would enable one to perform transition between spin-up and spin-down states within 2 ps. Highlights • Transient magnetic field generates the charge flow between inner and outer channels in double quantum ring. • Frequency of radial density oscillations is independent on frequency of magnetic pulse. • Spin-orbit interation activates radial density oscillations for longer durations of magnetic pulse. • Spin oscillations are generated in double ring by transient magnetic field if spin-orbit interaction is involved. • Spin oscillations pattern may have irregular or more regular pattern depending on initial, up or down, orientation of magnetic field. [ABSTRACT FROM AUTHOR]

The effect of electron-phonon coupling, onsite repulsive Coulomb interaction and temperature on the persistent current in a quantum ring is studied in the presence of Dresselhaus spin-orbit interaction. The quantum ring threaded by the Aharonov-Bohm flux is modelled by the one-dimensional Holstein-Hubbard-Dresselhaus Hamiltonian. The electron-phonon interaction and Dresselhaus spin-orbit interaction are decoupled by employing the Lang-Firsov coherent transformation and a unitary transformation respectively. Thereafter, a self-consistent diagonalization technique is performed numerically at the Hartree-Fock level to obtain the effective electronic energy and current. It is shown that the intrinsic Dresselhaus spin-orbit interaction enhances the persistent charge and spin currents significantly. On the other hand, the persistent current is reduced by the onsite and nearest-neighbour electron-phonon interaction and Coulomb interaction. Also, the behaviour of the currents is modified by temperature. The spin-splitting of persistent spin current is enhanced considerably by Dresselhaus spin-orbit interaction and this splitting is tuneable in different regimes of magnetic flux, temperature, chemical potential and the interactions present in the system. • A correlated polar quantum ring threaded by Aharonov-Bohm flux is considered. • Persistent charge and spin currents are calculated at finite temperature. • Effect of Dresselhaus spin-orbit interaction (DSOI) is investigated. • DSOI significantly enhances the charge and spin currents. • Dresselhaus interaction also increases the spin splitting which is tunable. [ABSTRACT FROM AUTHOR]

This paper presents a design strategy, their efficient visible light converting optimizations offsets and dye anchorage utility as N-doped fused ring electron acceptors of organic dye Y123 in photovoltaic and optical devices. Five novel dyes (Y1–Y5) are investigated, identifying major electronic contributions. Results shows favourable energy levels and oscillator strengths (f) for efficient charge transfer upon photoexcitation. The dye Y1 had an ionization potential (IP) of 3.00eV, electron affinity (EA) of 1.01eV, and dipole moment of 2.01D. The dye Y3 exhibited a high global hardness (η) of 0.85 and low softness (σ) of 0.12eV, indicating stability and strong electron-accepting ability. Evaluation of photovoltaic performance revealed impressive characteristics, such as Y2 with a light harvesting efficiency (LHE) of 98 %, open-circuit voltage of 1.74eV, fill factor of 0.9235, and short-circuit current (J sc) density of 50.92 mA/cm2, resulting in a maximum power output (P max) of 81.82W. This study also included a detailed analysis of transition density matrix (TDM) and electron-hole overlap, providing insights into exciton dissociation and charge separation mechanisms in Y123 dyes. These analyses enhance the design of efficient N-doped fused ring electron acceptors for organic photovoltaic and optical devices. The study demonstrates the potential of N-doped fused ring electron acceptors as promising materials for efficient energy conversion in next-generation organic photovoltaic and optical devices. • Developing electronically rich populations for organic dyes. • Enriching the electronic population of Y123 core with sp2 hybridization. • An observance of enhancement of optical and photovoltaic features. • A future possibility to pave the way for their synthetic designs. [ABSTRACT FROM AUTHOR]

• Hf 0.5 Zr 0.5 O 2 (HZO)-stacked negative capacitance field-effect transistor (NCFET) for possible beyond-CMOS technology. • Impact of ferroelectric domain numbers on the performance of MFM stack and HZO-NCFET device-circuit co-design. • HZO-NCFET offers significant voltage amplification compared to conventional PZT-NCFET and P(VDF-TrFE)-NCFET. • This study predicts that HZO has a switching time approximately 20 times faster than traditional ferroelectric Pb(Nb 0.04 Zr 0.28 Ti 0.68)O 3. • The HZO-NCFET-RO outperforms standard CMOS-RO, showcasing its potential for advancing beyond-CMOS technologies and guiding NCFET design optimization. This paper explores the performance of Hf 0.5 Zr 0.5 O 2 (HZO)-stacked negative capacitance field-effect transistor (NCFET) for possible beyond complementary metal–oxide–semiconductor (CMOS) technology. For the first time, we investigate the impact of ferroelectric (FE) domain numbers on the negative capacitance (NC) effect, energy dissipation, NC effect voltage window, polarization ramping rate, voltage amplification (A NC), and oscillation frequency of a 5-stage HZO-NCFET inverter-based ring oscillator (HZO-NCFET-RO). The results show that HZO-NCFET is suitable for low-voltage and high-speed applications, providing a significant increase in A NC concerning the conventional PZT-NCFET and P(VDF-TrFE)-NCFET. Our study suggests that the HZO intrinsic NC effect time scale is tiny and limited by the FE switching. We show that the switching time of HZO is ∼20 times faster than the traditional FE [Pb(Nb 0.04 Zr 0.28 Ti 0.68)O 3 ]. Finally, the proposed 5-stage HZO-NCFET-RO offers superior performance with a 26% higher oscillation frequency and a 94.42% reduction in power dissipation compared to standard 5-stage CMOS inverter-based RO. These findings highlight the potential of HZO-stacked NCFET as an alternative device for the future beyond-CMOS technology. [ABSTRACT FROM AUTHOR]

Highlights • Bi-doped SnO 2 hierarchical nanoflowers have been successfully synthesized. • Gas sensors based on Bi-doped SnO 2 exhibit superior sensing performance to HCHO. • The optimum operating temperature of Bi-doped SnO 2 is 170 °C. • 3D hierarchical nanostructures and Bi doping improve the gas sensing performance. Abstract In order to improve the gas sensing performance of traditional SnO 2 semiconductor nanomaterials, Bi-doped SnO 2 hierarchical flower-shaped nanostructures had been synthesized by a one-step hydrothermal route. Diverse techniques characterization results collectively revealed that Bi ions have been successfully doped into SnO 2 lattice and samples present numerous uniform flower-shaped nanostructures composed of many layered petal-like thin nanosheets. Benefiting from such unique 3D hierarchical flower-shaped nanostructures and Bi doping, the sensors based on Bi-doped SnO 2 exhibited superior gas sensing performance concluding higher response value, faster response/recovery time, good stability and excellent selectivity to HCHO at the optimum operating temperature of 170 °C. Therefore, Bi-doped SnO 2 hierarchical flower-shaped nanostructures could be used as a candidate semiconductor gas sensing materials for manufacturing highly sensitive HCHO gas sensors in the future. [ABSTRACT FROM AUTHOR]

Abstract ZnO micro/nanostructures with different morphologies were prepared though a solvothermal process in the presence of surfactants. The structures and compositions were investigated using various techniques, including X-ray diffraction (XRD), a scanning electron microscope (SEM), a UV–vis spectrophotometer, and a fluorimeter. SEM observations revealed that the as-synthesized ZnO samples exhibited nanospheres (NSs), hexagonal disks (HDs), hexagonal bilayer disk-like structures (HBDs), and 3D flower-like hierarchitectures (HAs) due to the effect of the surfactant. XRD results showed that the prepared samples were wurtzite hexagonal phase ZnO with good crystallinity. The band gap energy (E g) values of the ZnO samples were 3.24 eV, 3.20 eV, 3.15 eV, and 3.24 eV for the ZnO NSs, HDs, HBDs, and 3D HAs, respectively. The photocatalytic properties of the as-synthesized samples were investigated by measuring the degradation on the Rhodamine-B (Rh-B). Among them, the as-synthesized 3D ZnO HAs had the highest photocatalytic activity, which showed a degradation efficiency of 97.34% for Rh-B under UV irradiation. The excellent photocatalytic efficiency is attributed to the hierarchical structures and good crystallinity, which led to the efficient separation of photogenerated electrons and holes. [ABSTRACT FROM AUTHOR]

Abstract The capture cross-section, intersubband optical cross-section and non-radiative emission rates related to localized hole states are obtained for p-i-n solar cells containing GaSb/GaAs quantum rings embedded within the i-region of the device. The technique developed uses the intraband photoemission current to probe the charge state of the nanostructures during two-color excitation. Analysis of the excitation power dependence revealed a non-radiative hole capture lifetime of 12 ns under low excitation conditions, with high injection leading to the saturation of the hole occupancy within the quantum-rings. The decay characteristics of the optical hole emission current has also been exploited to determine the spectral and temperature dependence of the radiative and non-radiative hole escape mechanisms from the quantum-rings. Highlights • Power dependence of intraband photocurrent reveals quantum dot dynamics. • Two-color photoresponse correlated to capture/emission efficiency of nanostructures. • Optical and non-radiative carrier emission determined for type-II quantum structures. [ABSTRACT FROM AUTHOR]

Graphical abstract NiCoCrAlYTa coating, which possesses excellent oxidation resistance was prepared by HVOF spraying technology on the Inconel 718 substrate. And an oxidative layer with double-levels nanostructure formed on the surface of coating after different isothermal oxidation time, which presents excellent mechanical properties as well as friction and wear behaviors rate due to the the coupling effects of the gradient nanostructure of oxidative layer and the formation of amorphous protective layer on its worn surface. Highlights • The NiCoCrAlYTa coating exhibits excellent oxidation resistance in air at 1000 °C. • The oxidative layer of C3 presents double-levels structure. • The sample of C3 has excellent mechanical properties. • The friction and wear behaviors of C3 are obviously better than that of C1. • An amorphous layer forms on worn surface to improving its tribological properties. Abstract NiCoCrAlYTa coating, a metal-based coating, was prepared on Inconel 718 Ni-base superalloy substrate by high velocity oxy-fuel (HVOF) spraying. The as-polished NiCoCrAlYTa coating was heated at 1000 °C for different durations to afford coatings C1, C2, C3, and C4. The microstructure, element distribution, phase composition and crystalline structure of the as-deposited coating and heat-treated ones were analyzed by transmission electron microscopy, scanning electron microscopy-energy dispersive spectrometry, X-ray diffraction and electron back-scattered diffraction. Moreover, the oxidation behavior of the NiCoCrAlYTa coatings was evaluated based on isothermal oxidation kinetics as well as weight loss measurements; and the effects of surface oxide layers on the microstructure, mechanical properties as well as friction and wear behavior of the NiCoCrAlYTa coatings were investigated. Results show that the as-sprayed coating exhibits dense and uniform microstructure as well as excellent oxidation resistance. Oxide layers, mainly composed of Al 2 O 3 , Cr 2 O 3 , NiO, Y 2 O 3 , Ta 2 O 5 , NiCr 2 O 4 , and CoCr 2 O 4 , are formed on the surface of the coating upon heat-treatment in air; and the microstructure and mechanical properties of the NiCoCrAlYTa coatings as well as oxide layers are governed by heat-treatment time. Particularly, coating C3, obtained after heat-treatment of the as-polished NiCoCrAlYTa coating at 1000 °C for 50 h, exhibits greatly increased indentation hardness, elastic modulus, and wear resistance. This is because the joint functions of a compact and continuous surface oxide layer with gradient nanostructure formed after heat-treatment, and the amorphous protective layer generated on the rubbed surface of coating C3. [ABSTRACT FROM AUTHOR]

Hydrostatic pressure can be used as a powerful diagnostic tool to enable the study of lattice dynamics, defects, impurities and recombination processes in a variety of semiconductor materials and devices. Here we report on intermediate band GaAs solar cells containing GaSb quantum rings which exhibit a 15% increase in open-circuit voltage under application of 8 kbar hydrostatic pressure at room temperature. The pressure coefficients of the respective optical transitions for the GaSb quantum rings, the wetting layer and the GaAs bulk, were each measured to be ~ 10.5 ± 0.5 meV/kbar. A comparison of the pressure induced and temperature induced bandgap changes highlights the significance of the thermal energy of carriers in intermediate band solar cells. [ABSTRACT FROM AUTHOR]

The generation of tightly focused light beams carrying orbital angular momentum (OAM) offers new opportunities for applications in photonics, optoelectronics and optical communications. These spatially inhomogeneous light fields render possible the coupling of the photon field to the angular momentum characteristics of the sample. In this study we exploit this fact and consider nanostructured quantum rings (QRs) irradiated by OAM beams with the aim of inducing swiftly local magnetic moments as well as harmonic generation. Based on a time-dependent quantum simulation we investigate different laser setups for efficient magnetic moment generation during and after the pulse application. In particular, we study the role of the winding number of the optical vortex in enhancing the magnetic moment at a fixed laser intensity. Further, we analyze the emitted radiation associated with the photoinduced charge oscillations and the non-equilibrium current circulation. Irreversible relaxation processes due to the interaction of charged carriers with acoustic phonons are included using a density matrix formalism. [ABSTRACT FROM AUTHOR]

Influence of Rashba and Dresselhaus spin orbit interactions (SOIs) as well as external magnetic and electric fields on optical behaviors of quantum rings (QRs) were studied. To achieve this purpose, the matrix diagonalization method was exerted to compute energy eigenvalues of the system in the presence of electric and magnetic fields. Besides, the compact density matrix approach was used to calculate the refractive index (RI) and absorption coefficient (AC) of 1 → 2, 1 → 3, 1 → 6 and 3 → 5 transitions. Moreover, by increasing the magnetic (B) and electric (F) fields, energy splitting of intersubband energy levels was increased and thus the RIs and ACs of the system are changed. The results clearly show that, position and peak value of total RIs and ACs curves of all transitions experienced significant change by increasing the magnetic and electric fields in the presence of SOIs. Finally, the effect of size variation on optical RI changes and ACs was studied. The results show that the higher inner radii, R 1 , is, the stronger quantum confinement and energy increase are. These results are relevant for the designing of spin-based devices. [ABSTRACT FROM AUTHOR]

We consider the effects of interaction of a two-dimensional charged quantum ring with an ultra-short transient perpendicular magnetic field of duration below 10 ps. According to Faraday law, the time variations of magnetic field generate the rotational electric field in the ring, which however, as we show in a paper, can not induce the charge current along the channel of circular ring. It is because the magnetic field preserves the rotational symmetry of the confinement, and thus, can not mix the states of different angular momenta, albeit, the weak radial oscillations of the charge current can be still induced. We show, that the azimuthal component of charge current can be actually generated by an ultra-short magnetic pulse, provided that, the rotational symmetry of the ring is lifted by an in-plane electric field or when a spin-orbit interaction is taken into account. In both cases, the mixing of the angular momentum states is activated by the off-diagonal terms in Hamiltonian matrix. In the latter case, the change of angular momentum of the electron is accompanied by a rotation of its spin, and therefore, depending on an initial polarization of magnetic pulse, the final excitation energy may have a monotonic or an oscillatory character for a longer pulse duration. We conclude that proposed mechanism of fast excitation of charge carriers confined in quantum ring with an ultra-fast magnetic pulse can be applied for an ensemble of self-organized quantum rings, since, these are not usually perfectly circular while the strength of Dresselhaus spin-orbit interaction can be determined in advance, during their fabrication. Additionally, it allows for excitation of charge carriers without heating the sample what takes place if it is irradiated by a laser beam. [ABSTRACT FROM AUTHOR]

In this paper optical properties of a new QR based on MQWs have been investigated for detection in the THz range. The QR composed of a periodic effective quantum sites that each one considered as QW in theta direction. Using Tight binding method, eigen value problem for a QR with circumstance of 100 nm number with different number of wells i.e. 2, 4, 6 and 8 are solved and the absorption spectrum have been calculated. The results show that absorption has maximum value in range of (1.2–2.88 THz) that can be used for THz detection. Finally, it is realized that by increasing the number of wells, the numbers of absorption line also increase. [ABSTRACT FROM AUTHOR]

In this article, we report the formation of InAs quantum ring nanostructures (QRNs) on GaSb (0 0 1) surface by droplet epitaxy (DE) mode using molecular beam epitaxy. We examined the impact of various growth conditions, including substrate temperature (T s ), As 2 beam equivalent pressure (BEP) and surface stoichiometry, on the shape, density and size of the InAs QRNs. We confirmed that the InAs QRNs have better rotational symmetry at relatively high T s and low As 2 BEP. The symmetry of the QRN is due to the isotropic indium (In) out-migration along [1 1 0] and [1 −1 0], controlled via change in stoichiometry (surface As coverage) with temperature and the As 2 BEP. These results indicate that we can realize InAs QRN on GaSb surface by DE process. [ABSTRACT FROM AUTHOR]

Aim of this study is to investigate spin transportation in double quantum ring (DQR). We developed an array of DQR to measure the transmission coefficient and analyze the spin transportation through this system in the presence of Rashba spin-orbit interaction (RSOI) and magnetic flux estimated using S-matrix method. In this article, we compute the spin transport and spin-current characteristics numerically as functions of electron energy, angles between the leads, coupling constant of the leads, RSOI, and magnetic flux. Our results suggest that, for typical values of the magnetic flux ( ϕ / ϕ 0 ) and Rashba constant ( α R ), such system can demonstrates many spintronic properties. It is possible to design a new geometry of DQR by incoming electrons polarization in a way to optimize the system to work as a spin-filtering and spin-inverting nano-device with very high efficiency. The results prove that the spin current will strongly modulate with an increase in the magnetic flux and Rashba constant. Moreover it is shown that, when the lead coupling is weak, the perfect spin-inverter does not occur. [ABSTRACT FROM AUTHOR]

Using a variational approach, we have calculated the binding energies ( E 1 s , 2 s b ) and interband emission energy ( E p h ) of an exciton confined in G a A s / G a 1 − x A l x A s quantum rings (QRs) structures under effects of the temperature and pressure, in the effective mass approximation. We have taken into consideration the difference in the effective masses of the charge carriers in two materials, well and barrier. The results that we have obtained show clearly that E 1 s , 2 s b and E p h are influenced by the structure geometries of QR (height H , radial thickness Δ R and potential barrier), the temperature and pressure. Indeed, with a smaller geometric parameter, E 1 s , 2 s b and E p h become higher due to the improvement in confinement of the charge carriers. We have also observed that for a given value of the temperature, the pressure leads to an increasing of the E 1 s , 2 s b and E p h , and the latter quantities are decreasing with temperature. In addition, these variations of the E 1 s , 2 s b and E p h under the external perturbations are more remarkable in small H for fixed Δ R , and for larger Δ R for a given value of the H , because for the choice of a finite height of the barrier in the z direction and an infinite confinement in ρ direction. [ABSTRACT FROM AUTHOR]

We report on calculation of spin-dependent thermal transport through a quantum ring with the Rashba spin-orbit interaction. The quantum ring is connected to two electron reservoirs with different temperatures. Tuning the Rashba coupling constant, degenerate energy states are formed leading to a suppression of the heat and thermoelectric currents. In addition, the quantum ring is coupled to a photon cavity with a single photon mode and linearly polarized photon field. In a resonance regime, when the photon energy is approximately equal to the energy spacing between two lowest degenerate states of the ring, the polarized photon field can significantly control the heat and thermoelectric currents in the system. The roles of the number of photon initially in the cavity, and electron–photon coupling strength on spin-dependent heat and thermoelectric currents are presented. [ABSTRACT FROM AUTHOR]

We study the alteration of the magnetic and electric properties induced by the off-axis donor in a double InAs/GaAs concentric quantum ring. To this end we consider a model of an axially symmetrical ring-like nanostructure with double rim, in which the thickness of the InAs thin layer is varied smoothly in the radial direction. The energies and of contour plots of the density of charge for low-lying levels we find by using the adiabatic approximation and the double Fourier-Bessel series expansion method and the Kane model. Our results reveal a possibility of the formation of a giant dipole momentum induced by the in-plane electric field, which in addition can be altered by of the external magnetic field applied along the symmetry axis. [ABSTRACT FROM AUTHOR]

N doped MoS 2 quantum dots (QDs) are fabricated on large scale using a facile sintering/etching/exfoliation process we first proposed. Compared to pure MoS 2 and N-doped MoS 2 nanosheets, N-MoS 2 QDs exhibit high hydrogen evolution reaction (HER) activity with small onset overpotential of 82 mV, overpotential of 165 mV at 10 mA/cm 2 , a Tafel slope of 51.2 mV/dec and remarkable stability. The enhanced catalytic activity could be ascribed to the combination of increasing the active sites by reducing the size of MoS 2 and improving the conductivity of MoS 2 basal plane by chemical doping effect. This work paves a simplistic route for enhancing the HER activity of layered transition metal dichalcogenide based catalysts. [ABSTRACT FROM AUTHOR]

In this work we investigate magneto-optical properties of two-dimensional semiconductor quantum-ring excitons with Rashba and Dresselhaus spin-orbit interactions threaded by a magnetic flux perpendicular to the plane of the ring. By calculating the excitonic Aharonov-Bohm spectrum, we study the Coulomb and spin-orbit effects on the Aharonov-Bohm features. From the light-matter interactions of the excitons, we find that for scalar excitons, there are open channels for spontaneous recombination resulting in a bright photoluminescence spectrum, whereas the forbidden recombination of dipolar excitons results in a dark photoluminescence spectrum. We investigate the generation of persistent charge and spin currents. The exploration of spin orientations manifests that by adjusting the strength of the spin-orbit interactions, the exciton can be constructed as a squeezed complex with specific spin polarization. Moreover, a coherently moving dipolar exciton acquires a nontrivial dual Aharonov-Casher phase, creating the possibility to generate persistent dipole currents and spin dipole currents. Our study reveals that in the presence of certain spin-orbit generated fields, the manipulation of the magnetic field provides a potential application for quantum-ring spinor excitons to be utilized in nano-scaled magneto-optical switches. [ABSTRACT FROM AUTHOR]

We have theoretically studied the electronic and optical properties of a GaAs/AlGaAs elliptic quantum ring under in-plane electric field. The effects of an eccentric internal barrier -placed along the electric field direction, chosen as x -axis- and incident light polarization are particularly taken into account. The one-electron energy spectrum and wave functions are found using the adiabatic approximation and the finite element method within the effective-mass model. We show that it is possible to repair the structural distortion by applying an appropriate in-plane electric field, and the compensation is almost complete for all electronic states under study. For both concentric and eccentric quantum ring the intraband optical properties are very sensitive to the electric field and probe laser polarization. As expected, in the systems with eccentricity distortions the energy spectrum, as well as the optical response, strongly depends on the direction of the externally applied electric field, an effect that can be used as a signature of ring eccentricity. We demonstrated the possibility of generating second harmonic response at double resonance condition for incident light polarized along the x -axis if the electric field or/and eccentric barrier break the inversion symmetry. Also, strong third harmonic signal can be generated at triple resonance condition for a specific interval of electric field values when using y -polarized light. [ABSTRACT FROM AUTHOR]

Reduced graphene quantum dots (r-GQDs) coated gold nanoparticles (AuNPs) core-shell structure is developed as a nanosensor for highly selective and sensitive colorimetric detection of cysteine. The reduction of nitrogen doped GQDs (N-GQDs) by NaBH 4 produces r-GQDs, which serve as reductant for facilitating the conversion of HAuCl 4 to AuNPs. The abundant hydroxyl groups and amino groups of r-GQDs not only promote the reduction of Au (III) into Au (0), but also facilitate the effective coating of r-GQDs onto AuNPs. The obtained core-shell structured AuNPs@r-GQDs are well dispersed and exhibit an intensive surface plasma band at 525 nm. After the adsorption of Ag + on the surface of AuNPs@r-GQDs, cysteine as cross-linking agent induces the aggregation of AuNPs@r-GQDs and leads to their color change, which allows the sensitive colorimetric detection of cysteine and offers a detection limit low to 5.6 nM. More importantly, AuNPs@r-GQDs nanosensor exhibits very high detection selectivity towards cysteine against glutathione (GSH), even at a GSH concentration of 10000-fold higher than that of cysteine. The practicability of this nanosensor is demonstrated by the discriminative determination of cysteine in human plasma. [ABSTRACT FROM AUTHOR]

The effect of interdiffusion and magnetic field on confined states of electron and heavy hole as well as on interband absorption spectrum in a Ga 1− x Al x As/GaAs Gaussian-shaped double quantum ring are investigated. It is shown that both interdiffusion and magnetic field lead to the change of the charge carriers' quantum states arrangement by their energies. The oscillating behavior of the electron ground state energy as a function of magnetic field induction gradually disappears with the increase of diffusion parameter due to the enhanced tunneling of electron to the central region of the ring. For the heavy hole the ground state energy oscillations are not observable in the region of the values of magnetic field induction B = 0 − 10 T . For considered transitions both the magnetic field and the interdiffusion lead to a blue-shift of the absorption spectrum and to decreasing of the absorption intensity. The obtained results indicate on the opportunity of purposeful manipulation of energy states and absorption spectrum of a Gaussian-shaped double quantum ring by means of the post growth annealing and the external magnetic field. [ABSTRACT FROM AUTHOR]