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We examine the influence of quantum dot (QD) morphology on the optical properties of two-dimensional (2D) GaSb/GaAs multilayers, with and without three-dimensional nanostructures. Using nanostructure sizes from scanning transmission electron microscopy and local Sb compositions from local-electrode atom-probe tomography as input into self-consistent Schrödinger–Poisson simulations based on 8 × 8 k·p theory, we compute confinement energies for QDs, circular arrangements of smaller QDs, termed QD-rings, and 2D layers on GaAs substrates. The computed confinement energies and the measured photoluminescence emission energies increase from QDs to QD-rings to 2D layers, enabling direct association of nanostructure morphologies with the optical properties of the GaSb/GaAs multilayers. This work opens up opportunities for tailoring near to far infrared optoelectronic devices by varying the QD morphology. [ABSTRACT FROM AUTHOR]

Linear and nonlinear optical properties of GaSb quantum ring inside AlxGa1−xAs/GaAs/AlxGa1−xAs quantum well (QW) and AlAs/GaAs/InGaAs/AlAs double QW have been theoretically investigated. The effects of the Al concentration in the barrier, the widths of the layers, the position of the quantum ring inside the wells and the incident optical intensity on linear and nonlinear absorption and refractive index, associated to the ground excitonic state, have been explored. We found that by varying the different parameters of the studied structures and the incident optical intensity, one can manipulate the linear and nonlinear absorption coefficient and refractive index. These results make the studied systems a promising candidate for application in tunable nano-optoelectronic devices. [ABSTRACT FROM AUTHOR]

We prove that the sheaf Euler characteristic of the product of a Schubert class and an opposite Schubert class in the quantum K-theory ring of a (generalized) flag variety G/P is equal to q d , where d is the smallest degree of a rational curve joining the two Schubert varieties. This implies that the sum of the structure constants of any product of Schubert classes is equal to 1. Along the way, we provide a description of the smallest degree d in terms of its projections to flag varieties defined by maximal parabolic subgroups. [ABSTRACT FROM AUTHOR]

Systematic quantum chemical investigation of quercetin and selected eight mono- and bihydroxyflavonols is presented. Structural analysis based on the Density Functional Theory showed that the energetically preferred conformation of flavonols substituted at the C5 and C3 atoms by a hydroxyl group is stabilised via intramolecular hydrogen bonds occurring between the (C4)O···HO(3 or 5) atomic pairs. Depending on the hydroxyl group positions, energetically preferred torsional orientation of the phenyl ring with respect to the planar benzo-γ-pyrone moiety changed from 0 to 180 degrees. Gas-phase electron transitions were investigated using the time-dependent DFT treatment. The dependence of maximal wavelengths on the torsional deformation of the phenyl ring is of a similar shape, i.e. minima observed for the perpendicular orientation and maxima for the planar one. Shape and energies of the Highest Occupied (HOMO) and Lowest Unoccupied (LUMO) Molecular Orbitals were compared. The obtained theoretical results were compared with available experimental data. [ABSTRACT FROM AUTHOR]

We theoretically investigated the influences of the magnetic field and light polarisation on the electronic and optical properties of a GaAs/GaAlAs pseudo-elliptic quantum ring, modelled by an outer ellipsis and an inner circle, in the presence of the Rashba and Dresselhaus spin–orbit interactions and Zeeman effect. We show that Aharonov-Bohm oscillations of the energy spectrum are not affected by the presence of the Zeeman effect alone but, in the presence of Rashba and Dresselhaus spin–orbit couplings, the periodicity of certain levels becomes hardly definite. The Zeeman effect generally enhances/diminishes the separation levels produced by Rashba/Dresselhaus interactions (SOI) and when both types of SOI are considered, the effect depends on their relative strength. The magnetic field can trigger spin-flip for each type of spin–orbit interaction and Zeeman effect or their combination through anticrossings in the energy spectra. Our results reveal that the absorption spectra are very sensitive to the magnetic field and light polarisation. For all polarisations considered, the magnetic field increment leads to the redshift or blueshift of some particular peaks (an effect of this ring geometry) and a better separation of the peaks. The x-polarised light determines spectra with many small, but separated peaks while the circular polarised light leads to spectra with large peaks of high amplitude. [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]

The photoionization microscopy of the Rydberg Rb atom exposed to a continuous infrared radiation laser field is investigated based on the semiclassical open orbit theory. In contrast to the photoionization of the Rydberg hydrogen atom, the ionic core-scattering effect plays an important role in the photoionization of the Rb atom. Due to the core-scattering effect and the laser field, the electron trajectories become chaotic. A huge number of ionization trajectories from the ionic source to the detector plane appear, which makes the oscillatory pattern in the electron probability distribution become much more complicated. The ρ–θ curve on the detector plane exhibits a self-similar fractal structure for the ionization trajectories of the Rydberg Rb atom in the laser field. Due to constructive and destructive quantum interference of different electron trajectories, a series of concentric rings appear in the photoionization microscopy interference patterns on the detector plane. The electron probability density distributions on the detector are found to be changed sensitively with the scaled electron energy and the laser wavelength. Even as the detector plane is located at a macroscopic distance from the photoionization source, the photoionization microscopy interference patterns can be observed clearly. These calculations may provide a valuable contribution to the actual experimental study of the photoionization microscopy of non-hydrogenic Rydberg atom in the laser field. [ABSTRACT FROM AUTHOR]

Emerging theoretical concepts for quantum technologies have driven a continuous search for structures where a quantum state, such as spin, can be manipulated efficiently. Central to many concepts is the ability to control a system by electric and magnetic fields, relying on strong spin-orbit interaction and a large g-factor. Here, we present a mechanism for spin and orbital manipulation using small electric and magnetic fields. By hybridizing specific quantum dot states at two points inside InAs nanowires, nearly perfect quantum rings form. Large and highly anisotropic effective g-factors are observed, explained by a strong orbital contribution. Importantly, we find that the orbital contributions can be efficiently quenched by simply detuning the individual quantum dot levels with an electric field. In this way, we demonstrate not only control of the effective g-factor from 80 to almost 0 for the same charge state, but also electrostatic change of the ground state spin. Quantum technology concepts rely on efficient control of the system state, such as the electron spin. Here the authors present a mechanism for spin and orbital manipulation based on hybridizing quantum dot states at two points inside InAs nanowires, resulting in tunable quantum rings with giant controllable g-factors. [ABSTRACT FROM AUTHOR]

This study set out to introduce the optical nonlinearities of a intense laser-driven two-dimensional quantum ring subjected to external uniform magnetic field. Inclusion of the effect of non-resonant, high-frequency THz laser radiation is realised by the laser-dressed potential, whereas the total optical absorption coefficients, total relative refractive index changes and third-harmonic generation (THG) coefficient are inferred from the scheme of compact density-matrix formalism and iterative method. Our results reveal that the laser field smoothens the antidot region of the ring that consequences with remarkable modifications in the electronic structure and correspondingly the optical response of the system. We have found that the height and location of the resonant peaks of total optical absorption coefficient, total relative refractive index changes and THG coefficient can be controlled by the externally applied fields and system parameters. The tunability of the intersubband transitions could be beneficial for practical device application relying on the electronic optical transitions. [ABSTRACT FROM AUTHOR]

There is a special class of logic gates, called universal gates, any one of which is sufficient to express any desired computation. The NAND gate is truly global, given that it is already known, each Boolean function can be represented in a circuit that contains only NOT and AND gates, it is sufficient to show that these gates can be defined from the NAND gate. The effect of Rashba spin-orbit interaction (SOI) on the gate response and spin current density in a series of non-interacting one-dimensional rings connected to some leads is studied theoretically within the waveguide theory. The gates response and spin current density are computed in geometry of the system containing two terminal double quantum rings. Also, the presence and absence of Rashba SOI are treated as the two inputs of the AND/NAND/NOT gates. Furthermore, simulation of the device performance demonstrates that vital improvement toward spintronic applications can be achieved by optimizing device parameters such as magnetic flux and Rashba coefficient. [ABSTRACT FROM AUTHOR]

In this paper we study consequences of the results of Kang et al. [ Monoidal categorification of cluster algebras , J. Amer. Math. Soc. 31 (2018), 349–426] on a monoidal categorification of the unipotent quantum coordinate ring $A_{q}(\mathfrak{n}(w))$ together with the Laurent phenomenon of cluster algebras. We show that if a simple module $S$ in the category ${\mathcal{C}}_{w}$ strongly commutes with all the cluster variables in a cluster $[\mathscr{C}]$ , then $[S]$ is a cluster monomial in $[\mathscr{C}]$. If $S$ strongly commutes with cluster variables except for exactly one cluster variable $[M_{k}]$ , then $[S]$ is either a cluster monomial in $[\mathscr{C}]$ or a cluster monomial in $\unicode[STIX]{x1D707}_{k}([\mathscr{C}])$. We give a new proof of the fact that the upper global basis is a common triangular basis (in the sense of Qin [ Triangular bases in quantum cluster algebras and monoidal categorification conjectures , Duke Math. 166 (2017), 2337–2442]) of the localization $\widetilde{A}_{q}(\mathfrak{n}(w))$ of $A_{q}(\mathfrak{n}(w))$ at the frozen variables. A characterization on the commutativity of a simple module $S$ with cluster variables in a cluster $[\mathscr{C}]$ is given in terms of the denominator vector of $[S]$ with respect to the cluster $[\mathscr{C}]$. [ABSTRACT FROM AUTHOR]

The influence of exchange interaction on the transport properties of a two-dimensional diluted magnetic semiconductor quantum ring with finite width has been investigated in the presence of a uniform perpendicular magnetic field. The dependence of magnetoresistance on the magnetic field, Mn concentration, and quantum ring width are investigated. In the absence of exchange interaction, a typical beating pattern with well-defined node-positions in the oscillating magnetoresistance is observed. It was shown that in the present exchange interactions the beating pattern is destroyed. [ABSTRACT FROM AUTHOR]

Over the past few decades, superconducting circuits have been used to realize various novel electronic devices such as quantum bits, SQUIDs, parametric amplifiers, etc. One domain, however, where superconducting circuits fall short is information storage. Superconducting memories are based on the quantization of magnetic flux in superconducting loops. Standard implementations store information as magnetic flux quanta in a superconducting loop interrupted by two Josephson junctions (i.e., a SQUID). However, due to the large inductance required, the size of the SQUID loop cannot be scaled below several micrometers, resulting in low-density memory chips. Here, we propose a scalable memory consisting of a voltage-biased superconducting ring threaded by a half-quantum flux bias. By numerically solving the time-dependent Ginzburg-Landau equations, we show that applying a time-dependent bias voltage in the microwave range constitutes a writing mechanism to change the number of stored flux quanta within the ring. Since the proposed device does not require a large loop inductance, it can be scaled down, enabling a high-density memory technology. [ABSTRACT FROM AUTHOR]

In this paper, we study the quantum dynamics of an electron/hole in a two-dimensional quantum ring within a spherical space. For this geometry, we consider a harmonic confining potential. Suggesting that the quantum ring is affected by the presence of an Aharonov–Bohm flux and a uniform magnetic field, we solve the Schrödinger equation for this problem and obtain exactly the eigenvalues of energy and corresponding eigenfunctions for this nanometric quantum system. Afterwards, we calculate the magnetization and persistent current are calculated, and discuss influence of curvature of space on these values. [ABSTRACT FROM AUTHOR]

We show that for each k and n, the cyclic shift map on the Grassmannian Grk,n(C) has exactly nk fixed points. There is a unique totally nonnegative fixed point, given by taking n equally spaced points on the trigonometric moment curve (if k is odd) or the symmetric moment curve (if k is even). We introduce a parameter q∈C×, and show that the fixed points of a q‐deformation of the cyclic shift map are precisely the critical points of the mirror‐symmetric superpotential Fq on Grk,n(C). This follows from results of Rietsch about the quantum cohomology ring of Grk,n(C). We survey many other diverse contexts which feature moment curves and the cyclic shift map. [ABSTRACT FROM AUTHOR]

We present the solutions of the energy spectrum of charge carriers confined in a quantum ring in ABA-stacked trilayer graphene subjected to a perpendicular magnetic field. The calculations were performed in the context of the continuum model by solving the Dirac equation for a zero width ring geometry, i.e., freezing out the carrier radial motion. We show that the obtained energy spectrum exhibits different symmetries with respect to the magnetic field and other parameters. Moreover, the applied potential shifts the energy spectrum vertically while the applied magnetic field breaks all symmetries. We compare our results with those of the ideal quantum ring in monolayer and bilayer graphenes. [ABSTRACT FROM AUTHOR]

In this paper, we explore the linear, third-order nonlinear, and total optical absorption coefficient (OAC) and refractive index change coefficient (RICC) of a GaAs doped quantum dot/quantum ring (QD/QR) with parabolic-inverse squared potential in conjunction with modified Gaussian confinement and taking into account the presence of on-centre shallow donor and or acceptor impurity. Calculations are done via the compact density matrix formalism and the iterative method. The two-dimensional parabolic QD/QR is subjected to uniform magnetic field oriented perpendicularly to the plane of the structure. The energy levels and wave function are derived within the framework of effective-mass and parabolic band approximation. The results exhibit that the OACs and RICC are clearly affected by different parameters of the applied confinement, strength of magnetic field, and the presence of impurity. The variation of confinement potential, nature of impurity, dot radius, cyclotron frequency of the parabolic confinement potential, and geometric parameter of the on-centre repulsive potential lead to either a red-shift or a blue-shift of the resonant peaks of the OACs and of the maximum and minimum of the RICC together with significant variations of the magnitudes of these resonant structures. [ABSTRACT FROM AUTHOR]

An alternative strategy is proposed to achieve visible-blind ultraviolet (UV) monitoring. By introducing photochromic spiropyran (SP) molecules into the dielectric as the charge trapping layer, organic field-effect transistor (OFET) memories show a selective response to UV light and are inert to visible light. The photoisomerization of SP from the ring-close to ring-open states under UV illumination modifies its electronic structure, which facilitates electron trapping into the charge trapping layer and accordingly induces the memory effect. UV exposure recording can be realized by cumulative and nonvolatile electron trapping, enabling potential applications of OFET memories for UV monitoring in wearable electronics. [ABSTRACT FROM AUTHOR]

Spin Seebeck effect (SSE) in triple quantum dots coupled to ferromagnetic leads is studied by using the Keldysh nonequilibrium Green's function technique. In low temperature regimes, the Fano effect arising from the interferences between the isolated states and the continuum plays an dominant role in the electronic and thermoelectric transport processes. The Seebeck coefficient depends on spin degree of freedom when the leads' magnetic moments are in parallel configuration. When the leads' polarization is varied, the charge Seebeck coefficients are less influenced, whereas those of the spin counterparts are obviously changed. The magnitudes of both the SSE coefficient and the spin figure of merit (FOM) will be enhanced by increasing the asymmetry of the leads' spin polarization. In the presence of the spin-dependent interdot couplings, the strengths of the charge and spin thermoelectric quantities are individually suppressed and enhanced, and then the magnitudes of the SSE coefficient and the spin FOM are comparable to those of the charge counterparts. Interestingly, by the joint effects of the ferromagnetism on the leads and the spin-dependent interdot couplings, the spin thermopower can even changes its sign around the antiresonance states. [ABSTRACT FROM AUTHOR]

We report the controllable growth of GaAs quantum complexes in droplet molecular-beam epitaxy, and the optical properties of self-assembled AlxGa As quantum rings embedded in a superlattice. We found that Ga droplets on a GaAs substrate can retain their geometry up to a maximum temperature of 490 °C during post-growth annealing, with an optimal temperature of 320 °C for creating uniform and symmetric droplets. Through controlling only the crystallisation temperature under As4 in the range of 450 °C to 580 °C, we can reliably control diffusion, adsorption and etching rates to produce various GaAs quantum complexes such as quantum dots, dot pairs and nanoholes. AlxGa As quantum rings are also realised within these temperatures via the adjustment of As beam equivalent pressure. We found that crystallisation using As2 molecules in the place of As4 creates smaller diameter quantum rings at higher density. The photoluminescence of As2 grown AlxGa As quantum rings embedded in a superlattice shows a dominant emission from the quantum rings at elevated temperatures. This observation reveals the properties of the quantum ring carrier confinement and their potential application as efficient photon emitters. [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]

We discuss just infiniteness of C∗‐algebras associated to discrete quantum groups and relate it to the C∗‐uniqueness of the quantum groups in question, that is, to the uniqueness of a C∗‐completion of the underlying Hopf ∗‐algebra. It is shown that duals of q‐deformations of simply connected semisimple compact Lie groups are never C∗‐unique. On the other hand, we present an example of a discrete quantum group which is not locally finite and yet is C∗‐unique. [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]

Two photochromic room‐temperature ionic liquids (RTILs) based on anionic diarylethene derivative (DTE) were synthesized and characterized. Photochemical (quantum yields for ring closure and opening) and electrochemical (cyclic voltammetry) properties of the [ALIQUAT]2[DTE] and [P6,6,6,14]2[DTE] compounds as amorphous salts have been investigated. All compounds (including the di‐acid precursor and two RTILs) were studied in solution, in their intrinsically pure forms (RTIL as unique media) and in the solid state (BaSO4 support). Combination with larger organic cations can stabilize the closed‐ring form, apparently avoiding the formation of by‐products without photodegradation. It is observed that the closed‐ring reaction is faster in the case of RTILs comparing to the di‐acid starting material. The coloration switches between transparent (initial state) to purple ([ALIQUAT]2[DTE]) or pink ([P6,6,6,14]2[DTE]). The novel diarylethene‐based RTILs as multi‐coloured photochromic materials can open attractive perspectives for materials science applications. [ABSTRACT FROM AUTHOR]

Energy levels of electrons in the semiconductor circular quantum ring are obtained within the framework of perturbation theory in the presence of the Rashba and Dresselhaus spin-orbit interactions and external uniform constant magnetic field. The confinement effect is simulated by the realistic potential well of a finite depth. [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 We establish ring isomorphisms between quantum Grothendieck rings of certain remarkable monoidal categories C Q , B n and C Q , A 2 n − 1 of finite-dimensional representations of quantum affine algebras of types B n (1) and A 2 n − 1 (1) , respectively. Our proof relies in part on the corresponding quantum cluster algebra structures. Moreover, we prove that our isomorphisms specialize at t = 1 to the isomorphisms of (classical) Grothendieck rings obtained recently by Kashiwara, Kim and Oh by other methods. As a consequence, we prove a conjecture formulated by the first author in 2002: the multiplicities of simple modules in standard modules in C Q , B n are given by the specialization of certain analogues of Kazhdan-Lusztig polynomials and the coefficients of these polynomials are positive. [ABSTRACT FROM AUTHOR]

The ground state binding energy of hydrogenic donor impurity is calculated using the plane wave basis method in InGaAsP/InP quantum ring under applied electric and magnetic fields. The results show that the binding energy is nonlinear function of ring height and outer radius. The binding energy has a maximum near the center of radial or axial direction. The external electric field changes the probability distribution of electron, and then the difference of binding energies for impurity located at symmetrical positions increases. The binding energy increases with the increase of magnetic field and the effect of magnetic field is more obvious along the direction of magnetic field. [ABSTRACT FROM AUTHOR]

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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]

In this paper concerned with the solution of the nanoscale structures consisting of the InAs/GaAsvfith an effective mass envelope function theory, the electronic states of the InAs/GaAs quantum ring are studied.In calculations, the effects due to the different effective masses of electrons in and out the lings are included. The energy levels of the electron are calculated in the different shapes of rings, i.e.. that the inner radius of lings sensitively change the electronic states. The energy levels of the electron are not sensitively dependent on the outer radius for large lings. The structures of InAs/GaAs quantum lings are studied by the one electronic band Hamiltonian effective mass approximation, the energy-and position-dependent on electron effective mass approximation, and the spin-dependent on the Ben Daniel-Duke boundary conditions, hi the description of the Hamiltonian matrix elements, the Finite elements method with different base piecewise linear function is adopted. The non-linear energy confinement problem is solved approximately by using the Finite elements method with piecewise linear function, to calculate the energy of the one electron states for thelnAs/GaAs quantum ring. The results of numerical example are compared for accuracy and efficiency with the finite element method of linear triangular element. This comparison shows that good results of numerical example. [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]

This document is a correction notice for an article titled "Theoretical studies on the effects of pressure, temperature, and aluminum concentration on the optical absorption, refractive index and group velocity within GaAs/Ga1?xAlxAs quantum ring in the presence of Rashba..." published in the journal Optical & Quantum Electronics. The correction relates to an error in the grant number mentioned in the Acknowledgements section. The correct grant number is ISP23-66, provided by the deputyship for research & innovation, ministry of education in Saudi Arabia. Springer Nature, the publisher, remains neutral in terms of jurisdictional claims and institutional affiliations. [Extracted from the article]

• 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]