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This paper introduces a novel approach for the efficient determination of confined electron states in quantum semiconductor structures through the introduction of a generalized energy eigenvalue problem formulated within the framework of boundary integral analysis. The proposed method enables the direct determination of the energy eigenvalues and normalized wavefunctions for bound quantum states. The novel technique aims to address the challenges associated with efficiently modeling the behavior of electrons within confined regions, offering insights into optimizing the performance of a wide range of quantum semiconductor structures. By employing boundary integral techniques, the paper establishes an efficient numerical framework that effectively addresses the complexity of quantum confinement effects. The methodology is demonstrated through numerical simulations, showcasing its effectiveness and accuracy in predicting electron states within different quantum wire structures. [ABSTRACT FROM AUTHOR]

In the approximation of the effective mass, the electric field effect on the optical properties of the elliptical quantum wire (EQW) was investigated. In an elliptic coordinate system, exact solutions of the Schrödinger equation for an electron in an EQW with hard walls are obtained. The electron energy spectrum consists of even and odd energies states, whose wave functions are expressed through even and odd Mathieu functions of the first kind. Using these solutions, an orthonormal basis was constructed. The influence of the electric field perpendicular to the quantum wire and parallel to the ellipse's major axis on the energies and oscillator strength of quantum electron transitions was calculated using the matrix method. It is shown that the ellipticity of the quantum wire leads to the removal of the degeneracy of the energy spectrum of quasiparticles since the energies of even and odd electronic states depend differently on the ratio of the EQW semi-axes. The electron's ground state is the even state, which is nondegenerate because there is no corresponding odd state. The electric field has a greater effect on energy states with a lower value of the magnetic quantum number. As the electric field strength increases, the energies of even and odd states shift to the region of lower energies. [ABSTRACT FROM AUTHOR]

The fabrication and the optical properties of ultrathin GaN quantum wells on AlN (0001) vicinal surfaces with macrosteps are studied. The employed growth condition spontaneously restricts the GaN thickness to one monolayer (ML) on a planar plane. However, because of a higher density of dangling bonds at macrosteps, 2 ML GaN can be stabilized only at step edges, which creates quantum‐wire‐like 1D nanostructures with a dimension of a few nanometers for the lateral confinement. Exciton (carrier) confinement within the 1D GaN nanostructure is predicted theoretically and is confirmed experimentally by strongly polarized photoluminescence with in‐plane twofold symmetry at a wavelength of ≈250 nm at room temperature. This study demonstrates one path to realize quantum confinement within a fine nanoarchitecture composed of nitride semiconductors and might provide clues to the future creation of novel low‐dimensional nanostructures for the UV–vis spectral range. [ABSTRACT FROM AUTHOR]

The density functional theory is used to study the electronic structure of a quantum wire in a magnetic field. In a GaAs quantum wire, a critical density has been found, below which the electron density distribution has a strong spatial inhomogeneity. The effect of the disorder potential on the electron density profile in a two-dimensional electron gas is estimated. [ABSTRACT FROM AUTHOR]

In this paper, a GaAs quantum wire is considered with a semi-parabolic lateral confinement potential in the presence of a crossed electromagnetic field with the inclusion of Rashba SOI. The effects of pressure on thermodynamic properties have been studied. To this end, first, the eigenenergies for the system have been calculated considering Rashba spin effects under electric and magnetic fields. Then a numerical analysis is done to derive the partition function and obtain the system's thermodynamic properties. The results show that at low temperatures, all four thermodynamic properties don't show much effect due to pressure. It is found that entropy increases with increasing hydrostatic pressure, whereas pressure affects mean energy and free energy in a different manner. A peak structure is observed in specific heat as a function of temperature where the peak position depends on hydrostatic pressure. [ABSTRACT FROM AUTHOR]

Abstract We study the ground-state properties of quasi-one-dimensional paramagnetic electron fluid using variational quantum Monte Carlo method. The electrons are transversally confined using the harmonically regularized Coulomb potential with long range order. In this work we have investigated the crossover from liquid to crystalline phase in the finite width paramagnetic quantum wire. The calculated pair correlation function shows the oscillations of period $$2r_\text {s} a_0$$ 2 r s a 0 , where $$a_0$$ a 0 is the Bohr’s radius and $$r_\text {s}$$ r s is Wigner Seitz radius or electron-density parameter which corresponds to a $$k=4k_\text {F}$$ k = 4 k F peak with $$k_\text {F}$$ k F being Fermi wave vector in the static structure factor at finite electron density. It is a signature of the onset of Wigner crystallization. It is found that the cross-over from liquid to a quasi-Wigner phase is due to enhancement of the electron correlation effects as $$r_\text {s}$$ r s increases or as the wire width b decreases.

In this work, the thermodynamic properties of a Ga1-χAlχAs quantum wire under a parabolic confinement potential, influence of Rashba SOI and presence of Al impurity are studied. External electric and magnetic fields have also been considered. We first formulate the Hamiltonian of the system and then find the eigenenergies, which are used to calculate the partition function. The partition function is the basis of formulating the thermodynamic properties under consideration, viz. mean energy, heat capacity, free energy, entropy and magnetocaloric effect, which are plotted against temperature and impurity. The results show that the mean energy rises with temperature, a peak structure is observed in the heat capacity and the magnetocaloric effect, the free energy steadily decreases with temperature, and the entropy first increases, and then converges to a constant value. The mean energy, heat capacity and free energy increase with impurity, whereas the magnetocaloric effect decreases. The behaviour of all the properties with respect to impurity reverses when the value of impurity becomes greater than ~ 0.6. [ABSTRACT FROM AUTHOR]

A multichannel quantum tunneling of an electron stream through a potential barrier of a thin defect embedded in a quantum wire is theoretically considered. The electrons are also influenced by a magnetic field embedded in a quantum wire. Analytical expressions for the scattering coefficients and the spin polarization coefficient are obtained. It is shown that the electrons are fully polarized independently of other system parameters in certain energy intervals of each tunneling scattering channel. Any given degree of polarization can be obtained by controlling the energy spectrum with the use of a magnetic field. [ABSTRACT FROM AUTHOR]

We study the influence of the phase-change material VO2 on transverse magnetic (TM) surface plasmon (SP) modes in metallic arm-chair graphene nanoribbon (AGNR) qubits in the Lindhard approximation. We assess the effects of temperature as a dynamic knob for the transition from the insulating to the metallic phase on the TM SP modes in single-band (SB) and two-band (TB) transitions. We show that a VO2 substrate leads to TM SP modes in both SB and TB transitions. In addition, we observe that the SP modes have a lower frequency than those for a substrate of constant permittivity. In addition, we study the influence of the substrate-induced band gap Δ ′ on SP modes in TB transitions for the insulating and metallic phases of VO2. [ABSTRACT FROM AUTHOR]

We implement the lasing eigenvalue problem (LEP) approach to study the electromagnetic field in the presence of a circular quantum wire (QW) made of a gain material and wrapped in graphene cover and a dimer of two identical graphene-covered QWs, at the threshold of stationary emission. LEP delivers the mode-specific eigenvalue pairs, namely the frequencies and the threshold values of the QW gain index for the plasmon and the wire modes of such nanolasers. In our analysis, we use quantum Kubo formalism for the graphene conductivity and classical Maxwell boundary-value problem for the field functions. The technique involves the resistive boundary conditions, the separation of variables in the local coordinates, and, for the dimer, the addition theorem for the cylindrical functions. For single-wire plasmonic laser, we derive approximate engineering expressions for the lasing frequencies and threshold values of the gain index that complement the full-wave computations. For the dimer, we derive separate determinantal equations for four different classes of symmetry of the lasing supermodes and solve them numerically. Our investigation of the mode frequencies and thresholds versus the graphene and QW parameters shows that plasmon modes or, for the dimer, plasmon supermodes have lower frequencies and thresholds than the wire modes provided that the QW radius is smaller than 10 ÎĽ m, however in thicker wires they are comparable. Only the plasmon-mode characteristics are well-tunable using the graphene chemical potential. In the dimer, all lasing supermodes form closely located quartets, however, they quickly approach the single-wire case if the inter-wire separation becomes comparable to the radius. These results open a way for building essentially single-mode plasmonic nanolasers and their arrays and suggest certain engineering rules for their design. [ABSTRACT FROM AUTHOR]

We study the effect of the phase-change material VO 2 on plasmons in metallic arm-chair graphene nanoribbons (AGNRs) within the random-phase approximation (RPA) for intra- and inter-band transitions. We assess the influence of temperature as a knob for the transition from the insulating to the metallic phase of VO 2 on localized and propagating plasmon modes. We show that AGNRs support localized and propagating plasmon modes and contrast them in the presence and absence of VO 2 for intra-band (SB) transitions while neglecting the influence of a substrate-induced band gap. The presence of this gap results in propagating plasmon modes in two-band (TB) transitions. In addition, there is a critical band gap below and above which propagating modes have a linear negative or positive velocity. Increasing the band gap shifts the propagating and localized modes to higher frequencies. In addition, we show how the normalized Fermi velocity increases plasmon modes frequency. [ABSTRACT FROM AUTHOR]

Doping is fundamental to controlling the properties of bulk semiconductors. Although the antimony (SbV)‐doping strategy is widely employed in the design of practical tin oxide (SnO2) semiconductor gas sensors for higher signal‐to‐noise ratio, challenges remain to dope semiconductor nanocrystals since the diffusion of impurity atoms may be far from realized at the synthesis temperatures used. Herein, a metastable Sb‐doping strategy is proposed to overcome the serious receptor‐versus‐transducer mismatch in SnO2 quantum wires (QWs). The solvothermal synthesis of colloidal SbIII‐doped SnO2 QWs has been conducted at 180 °C, whereby the antimony amount is varied to optimize the structural and morphological properties for higher surface activity and electrical conductivity. A unique n‐type doping mechanism arising from the stable presence of SbIII on SnO2 (101) facets via SnII‐O‐SbIII is demonstrated. Further, the use of sensitive (down to 4 ppb, the lowest detection limit ever reported), fast (response and recovery time of 43 s and 96 s toward 10 ppm of H2S) gas sensors for H2S detection at near room temperature (40 °C) is showcased. The metastable Sb‐doping strategy may pave the way to ultrasensitive gas sensor possessing low power consumption and excellent integration compatibility to satisfy the increasing demand for ubiquitous and reliable gas detection. [ABSTRACT FROM AUTHOR]

The optical absorption coefficient in GaAs/AlGaAs cylindrical parabolic quantum wire (QW) with an applied static-electric field is studied in detail. The Schrödinger equation is solved within the effective mass approximation and an analytical solution is used for the electronic structure of cylindrical QW. The main aim is to clarify the effect of the Coulomb interaction on the exciton-related optical absorption of a QW with no assumptions about the strength of the confinement. Finally, it is clearly shown that the further confinement due to Coulomb interaction in a quantum wire increases the transition energy, dipole matrix elements, and absorption peaks, and results with the blue shift. One cannot neglect the Coulomb interaction in the absorption calculations. [ABSTRACT FROM AUTHOR]

We study the influence of the phase-change material VO2 on transverse magnetic (TM) surface plasmon (SP) modes in metallic arm-chair graphene nanoribbon (AGNR) qubits in the Lindhard approximation. We assess the effects of temperature as a dynamic knob for the transition from the insulating to the metallic phase on the TM SP modes in single-band (SB) and two-band (TB) transitions. We show that a VO2 substrate leads to TM SP modes in both SB and TB transitions. In addition, we observe that the SP modes have a lower frequency than those for a substrate of constant permittivity. In addition, we study the influence of the substrate-induced band gap Δ′ on SP modes in TB transitions for the insulating and metallic phases of VO2.

The binding energies of the heavy-hole and light-hole excitons in a cylindrical quantum wires composed of coaxial Als/GaAa/Alx1Ga1-x1-x/GaAs/Alx2Ga1-2 layers from inside to outside are calculated under the external electric fields. The numerical calculations were carried out by combining 4th order Runge-Kutta method and variational approaches. The exciton binding energies were found as functions of inner GaAs wire thicknesses and the external electric field strengths. The results show that, the exciton binding energies exhibit sharp changes at the certain values of structural parameters and the electric field has significant effects on the binding energies. These properties are thought to be useful technological applications. [ABSTRACT FROM AUTHOR]

We study the effect of the phase-change material VO2 on plasmons in metallic arm-chair graphene nanoribbons (AGNRs) within the random-phase approximation (RPA) for intra- and inter-band transitions. We assess the influence of temperature as a knob for the transition from the insulating to the metallic phase of VO2 on localized and propagating plasmon modes. We show that AGNRs support localized and propagating plasmon modes and contrast them in the presence and absence of VO2 for intra-band (SB) transitions while neglecting the influence of a substrate-induced band gap. The presence of this gap results in propagating plasmon modes in two-band (TB) transitions. In addition, there is a critical band gap below and above which propagating modes have a linear negative or positive velocity. Increasing the band gap shifts the propagating and localized modes to higher frequencies. In addition, we show how the normalized Fermi velocity increases plasmon modes frequency.

In this work the change in energy dispersion curve and ballistic conductance for InAs tunnel-coupled double quantum wire (DQWR) under the influence of the external magnetic field, electric field, hydrostatic pressure, temperature, and Rashba spin-orbit interaction (SOI) are studied theoretically in detail. A constant magnetic field transverse to the fundamental plane is applied to the DQWR. The Landuer-Büttiker formalism is used to determine the transport characteristics, and the energy eigenvectors and eigenvalues are derived within the parameters of the diagonalization approach. The numerical results indicate that the energy spectra of the system are influenced by external factors such as magnetic field, electric field, temperature, hydrostatic pressure, and Rashba SOI, resulting in variations in lateral/vertical and downward/upward shifts. These factors also cause oscillatory patterns in ballistic conductance due to the oddity of energy subbands. These results have significant implications for the advancement of double-quantum wire-based devices. [ABSTRACT FROM AUTHOR]

A considerable amount of work is done on nonlinear optical properties in quantum wells and dots. However, relatively fewer work is done on both quantum well wires and the excitonic effects. This work analyzes the excitonic effects on the refractive index change in quantum well wire. Our main effort is to make the effect of the Coulomb interaction more apparent. The density-matrix approach obtains the analytical expressions for the relevant optical coefficients. We have found that the Coulomb interaction plays a key role in the position and the height of the peaks of optical coefficient curves. Our findings show the way to optimize the nonlinear optical coefficients. [ABSTRACT FROM AUTHOR]

Fluctuations in the conductance are due to quantum diffusion through impurities in materials. If the material is weakly disordered, and if the size where current flows is smaller than the localization length, the conductance fluctuates around a universal value. This phenomenon is known as Universal Conductance Fluctuation (UCF). The fluctuations in the conductance are measured by the correlation function of the conductance, which can be evaluated diagrammatically. The expressions for the correlation function of the conductance from the conventional theory of transport in metals and its generalization in a strong magnetic field are revisited. An exact solution is provided for both expressions. We show that the exact value of the statistical variance of the conductance is 〈 Δ g 2 〉 = 8 / 15 (e 2 / h) 2 in one dimension. • The theory of transport in metals provides the conductance correlation function. • Its generalization in a magnetic field does not agree with the conventional theory. • The conductance correlation function in a magnetic field is corrected in this work. • The exact correlation function is derived for a quasi-one-dimensional material. • 〈 Δ g 2 〉 in one dimension is provided. [ABSTRACT FROM AUTHOR]

The results of theoretical modeling from the first principles of atomic structure and properties of promising low-dimensional structures from semiconductors, performed for the past five years at the Center of Nanoelectronics and Novel Materials of Belarusian state university of informatics and radioelectronics, are summarized. The discovered principal new properties of two-dimensional structures from dichalcogenides of refractory metals and semiconductor silicides, one-dimensional structures of silicon, А3В5 semiconductors and semiconductor metal oxides, and zero-dimensional structures of carbon - nanodiamonds - are presented.

The surface structural characteristics of Fe quantum wires prepared by two electrochemical methods in solution were studied by their conductance changes caused by the interactions between the quantum wires and specific molecules. Once ascorbic acid was added into the solution, the conductance of the Fe junction decreased to a lower value while for the dopamine adsorption, the conductance showed no obvious change. We proposed that there were some iron(II) ions on the surface of atomic-scale Fe junction, not iron(III) ions, and these iron(II) ions played a significant role for the conductance change. This mechanism was further enhanced by the following two experiments. When exposing the quantum wire to sodium borohydride, the conductance increased to a higher value, and the conductance increase was also observed with an electrochemical reduction process, which provided additional evidence for the proposed mechanism. [ABSTRACT FROM AUTHOR]

The electronic transport in an infinite arrays of driven quantum wells coupled to a quantum ring is studied via a single-band tunneling tight-biding Hamiltonian by perturbing and numerical simulations approaches. In the perturbing approach, an analytical relationship in terms of the coupling constants between nearest-neighbors in quantum wire coupled to a ring based on the quantum dynamical algebra is obtained. With a choice of three wells on the quantum ring, the transmission probabilities of electron of the number zero well of an wire under the effect of a constant field to the first, second and third well of quantum ring has been obtained for different values of the nearest-neighbors coupling constants in wire and quantum ring of the system. The effect of changes these parameters on the location and height of the first peaks related to the diagrams of transmission probability have been studied.

The influence of the cross-sectional shape of a quantum filament on the energy spectrum of electrons is studied. The calculation of energy levels of electrons in a quantum wire is performed. For the AlxGa1 - xAs quantum wire with infinite and finite depths, energy level spectra were obtained. The dispersion dependence with a parabolic law in a quantum wire with finite and infinite height of the potential barrier based on Al0.25Ga0.75As and Al0.75Ga0.25As was calculated, and graphs of dispersion dependences were obtained. The results are obtained for the linear sizes of a quantum wire from 5 nm to 15 nm. The transverse dimensions of cylindrical and rectangular quantum wires with close energy levels are found. The analysis of energy levels in cylindrical and rectangular quantum wires is carried out, and their similarities are revealed. It is shown that the energy levels are close to each other when the cross-sectional areas of rectangular and cylindrical quantum wires become equal. The solutions of the Schrödinger equation are presented, when the solution for a cylindrical wire can be replaced by the solution for a rectangular wire. [ABSTRACT FROM AUTHOR]

Quantum dot cellular automata (QCA) constitute an emergent nanoscale-based digital nanoelectronics technology with comprehensive applications in nanocomputing based on the small nanometer size of such circuits and their ultralow power consumption, fast operation, and high clock frequency in comparison with transistor-based complementary metal–oxide–semiconductor (CMOS) technologies. A novel design for edge-triggered synchronous J-K flip-flop (FF) and D (data or delay) flip-flop memory elements based on QCA cells with quantum wires is presented herein. The proposed design has fewer QCA cells and lower latency and area and uses the coplanar crossover method to overcome the complexity of multilayer quantum wire crossing. The design is analyzed to determine the average output polarization (AOP) of the edge-triggered synchronous D-FF and JK-FF at different temperature levels and the optimized energy dissipation. The layout design and computational simulation of the circuit are carried out using QCADesigner V. 2.0.3 software, while the energy dissipation is analyzed using the QCADesigner-E V. 2.2 tool. [ABSTRACT FROM AUTHOR]

The electron effective mass in GaAs quantum wires has been estimated by using a full dynamical random-phase approximation to examine its properties versus spin polarization, temperature, and carrier density. A decrease of mass with spin polarization is seen. The minority mass increases with the polarization while the majority mass decreases and this behaviour is seen for all densities. A maximal enhancement of mass at moderate temperature around 25 K is also presented. These calculations show a qualitative consistence with results in two-dimensional systems and help to control the electronic transport in quantum wires. • Spin and temperature dependence of quantum wire is analyzed. • Majority mass increases with spin polarization while minority mass decreases. • Majority mass is significantly enhanced below 50 K and peaks at 25 K. • Consistent results with two-dimensional values are seen. [ABSTRACT FROM AUTHOR]

Abstract We propose to explore analytically one of the most promising effects (soliton) for future applications in optical communication processing and memory devices, due to the nonlinearity inside low dimensional semiconductor systems. We focus on soliton propagation in microcavity wires. We derive analytical exact solutions that describe the stationary states of the soliton's profile in the cavity. We present a scheme that gives such profiles for a given external confining potential. The obtained profiles compare favorably with existing experimental and numerical results. [ABSTRACT FROM AUTHOR]

Abstract The theory of energy loss rate of non-equilibrium electrons due to inelastic interaction with intravalley piezoelectric phonons in a nano-dimensional semiconductor wire has been developed under the condition of low lattice temperatures, without recourse to the standard approximations which are usually made when developing theories at relatively higher temperatures. Such approximations are hardly valid when the lattice temperature is low. As expected, compared to the well-known earlier results, the theory here, reveals a complex and altogether different dependence of the energy loss rate upon the carrier energy and the lattice temperature. The numerical results have been obtained for narrow channel wires of GaAs and GaN. On comparison with other available results, it is revealed that the finite energy of piezoelectric phonons and the full form of the phonon distribution bring about quite significant changes in the energy loss characteristics at low temperatures. Highlights • Piezoelectric interaction in quantum wires studied. • Traditionally one assumes elastic collisions and equipartition law for phonons. • Theory of energy loss rate of non-equilibrium electrons is developed. • Effects of finite phonon energy and true phonon distribution are considered. • Characteristics for wires of GaAs and GaN differ significantly from traditional one. [ABSTRACT FROM AUTHOR]