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Impurity-induced absorption of light in quantum wires in the presence of external collinear electric and magnetic fields directed perpendicular to the nanowire axis is studied theoretically. The dopants in the quantum wire are modeled by a zero-radius potential. Expressions governing the light absorption coefficient are derived, and specificities of impurity light absorption are studied for all possible directions of polarization of the light wave. In particular, some of optical transitions that are forbidden in the absence of fields become allowed in the presence of external fields. Frequency dependences of light-absorption coefficient, along with the influence of electric and magnetic fields on the magnitude of absorption induced by impurities, are investigated. The possibility of controlling optical characteristics of nanowires by means of an electric field is demonstrated.

We study the effect of disorder and dephase in transmission of a CdS quantum wire using the Green’s function technique. Our results show that the transmission decreases with the increasing disorder strength. The resistance of a CdS quantum wire with phase-breaking scattering only increases with increasing dephasing. Obtained results show that the drain current of a CdS quantum wire with inelastic scattering by phonons with energy $$\hbar \omega = 30$$ meV decreases with the increasing disorder strength. Moreover, our theoretical results are independently supported by simulations of CdS disordered quantum wires based on a tight-binding model.

Optical polarization is an indispensable component in photonic applications, the orthogonality of which extends the degree of freedom of information, and strongly polarized and highly efficient small-size emitters are essential for compact polarization-based devices. We propose a group III-nitride quantum wire for a highly-efficient, strongly-polarized emitter, the polarization anisotropy of which stems solely from its one-dimensionality. We fabricated a site-selective and size-controlled single quantum wire using the geometrical shape of a three-dimensional structure under a self-limited growth mechanism. We present a strong and robust optical polarization anisotropy at room temperature emerging from a group III-nitride single quantum wire. Based on polarization-resolved spectroscopy and strain-included 6-band k·p calculations, the strong anisotropy is mainly attributed to the anisotropic strain distribution caused by the one-dimensionality, and its robustness to temperature is associated with an asymmetric quantum confinement effect.

Semiconductor nanowires are attractive building blocks of optoelectronics due to high efficiency and optical controllability. In particular, the mutual controllability of wavelength and polarization of light is essential for versatile applications such as displays, precise metrology, and bioimaging. We present quantum wire network emitters embedded in a single microrod capable of exhibiting orthogonally polarized dual-wavelength visible light at room temperature. The InGaN/GaN shell layers were grown on a single hexagonal GaN core microrod, spontaneously forming site-selective In-rich InGaN quantum wires on each edge between the nonpolar facets as well as each boundary between the nonpolar and semipolar facets. The orthogonally self-arranged, two sets of six quantum wires formed on the edges and the boundaries showed efficient violet and blue-green color emissions with strong linear polarization parallel and perpendicular to the c-axis at room temperature, respectively. This intriguing emission from a single microrod allows us to mutually manipulate the color and the polarization of light, which would be beneficial for photonic applications with unprecedented controllability and functionality.

The energy spectrum and optical absorption in a quantum wire of monolayer transition metal dichalcogenides in the shape of a straight strip are investigated theoretically. It is established that edge-like states with energies within the band gap of an infinite sample are absent in strips whose width is smaller than the critical one. Depending on the mutual parity of the quantum-confinement subbands in the valence and conduction bands, optical transitions are characterized by significantly differing threshold behaviors of the absorption strength. The strongest absorption corresponds to transitions between subbands with the same indices.

We use the Lasing Eigenvalue Problem (LEP) approach to study the source-free problem of the electromagnetic field in the presence of a circular quantum wire (QW) wrapped in graphene cover. Our instrument is the method of separation of variables and the Kubo formalism for the graphene conductivity. We analyze the lasing conditions for the plasmon modes of such a laser with microsize and nanosize QW diameters. We find eigenvalue pairs, i.e. the frequencies and the threshold values of the QW gain index for several plasmon modes and investigate their dependences on the QW and graphene parameters.

Core-shell nanostructures are highly attractive; their electrical and optical properties can be tuned by engineering their shapes and types of core-shell materials to achieve optimal nanomaterials for a variety of applications. Unfortunately, in the synthesis process of core-shell structures, geometric defects may unintentionally happen and possibly lead to undesired properties. In this Letter, the defect due to eccentricity in a core-shell square quantum wire is numerically investigated using the finite difference approach. The effects of the core shifting diagonally and vertically on optical transitions are reported. The results show that even a small core shift causes fully polarization-dependent transitions. The shift also affects the splitting of absorption coefficients due to x - and y -polarized light, leading to polarization-selective absorption in some photon energy ranges. As a result, the considered quantum wire is an alternative structure for polarizing light or detecting polarized light.

Electron transition rates due to interaction with circularly polarized light incident along the axis of a free-standing solid cylindrical nanowire are evaluated in the dipole approximation. The electric confinement potential of the nanowire is modeled as a superposition of two parts, in general, of different strengths; viz; parabolic and inverse parabolic in the radial distance. Additional confinement of the charge carriers is through the vector potential of the axial applied magnetic field. In systems with cylindrical symmetry, the electronic states are in part characterized by azimuthal quantum numbers: m=0, ±1, ±2,..., which in the absence of the axial applied magnetic field are doubly degenerate. In the dipole approximation and for circularly polarized light the selection rules are such that optical transitions are allowed between electronic states whose azimuthal quantum numbers differ by unity. Transition rates are characterized by peaks whenever the energy of the incident electromagnetic radiation matches transition energies for states between which transitions occur. The parabolic potential blue shifts peak of transition rates while the inverse parabolic potential redshifts the peaks. Results also indicate that transition rates are higher in nanowires of smaller radii. The homogeneous magnetic field lifts the double-degeneracies of electrons with opposite angular momenta, which leads to the emergence of two branches of the transition rates.

Electron mobility limited by surface roughness scattering in free-standing GaAs thin ribbon with an internal parabolic quantum well caused by surface state is investigated in detail. Based on analyzing the parabolic quantum well including the energy subband level, wave function and the confined potential profile in the thin ribbon by solving Schrödinger and Poisson equations self-consistently, the electron mobility could be investigated. Conclusion indicates that remote surface roughness (RSR) of the thin ribbon will change the two dimensional electron gas (2DEG) mobility through the medium of barrier height fluctuation of the parabolic well in atomic scale. Calculation results reveal that the 2DEG mobility decreases with increasing roughness amplitude, which is characterized in terms of the surface roughness height and the roughness lateral size.

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.

The role of hydrostatic pressure and temperature on the optical properties of a two dimensional electron gas confined in a quantum wire having Rashba spin orbit interaction is studied in this work. The energy band gap and thus the effective mass of the charge carriers are found to have strong dependence of the hydrostatic pressure on the quantum wire and its absolute temperature. This in turn affects the linear as well as the nonlinear optical properties of the quantum wire. The external magnetic field, temperature, hydrostatic pressure and the Rashba spin orbit interaction are found to interplay in determining the linear and nonlinear absorption coefficient and refractive change in the quantum wire as a response to incident electromagnetic radiation.

In the present work, we have theoretically studied the optical properties of a InAs quantum wire with dome cross section. We have used a numerical method which is based on a combination of coordinate transformation and the finite difference method. For this purpose, we have used analytical expressions for optical properties obtained by the compact-density matrix formalism. We have evaluated the linear, non-linear and the total absorption coefficients between the ground state for electron and heavy hole as a function of photon energy. The linear, non-linear and total refractive index changes are also investigated. These optical properties are determined with varying the incident optical intensity and the height of the wire.

Interaction of external acoustic waves - confined electrons - internal phonons in a cylindrical quantum wire with an infinite potential (CQWIP) has been theoretically studied via the quantum kinetic equation for electrons in the presence of an external magnetic field (EMF). The quantum kinetic equation for the distribution function of electrons interacting with internal and external acoustic phonons is obtained from the Heisenberg equation of motion and the model of CQWIP. The density of acoustomagnetoelectric (AME) current and the analytical expressions for the AME field in the CQWIP in the presence of the EMF are obtained. The theoretical results are numerically evaluated for the specific CQWIP of GaAs/GaAsAl. It is shown that the AME field strongly depends on the system temperature in both cases of the strong magnetic field and the weak magnetic field. However, the graph showing the relationship between the AME field and the system temperature has the peaks in case of the strong magnetic field. The reason may be due to movement of the electrons between the mini-bands. The AME field obtained in this work are then compared with those of bulk semiconductors, superlattices, quantum wells (QW) and rectangular quantum wire (RQW).

Using the combination of coordinate transformation and the finite difference method, we have studied theoretically, the optical absorption coefficient and the refractive index changes of the InAs/InP quantum wire, with a lens cross-section. For this purpose, we have used the analytical expressions for optical properties obtained by the compact-density matrix formalism. The evaluation has been performed in varying the dimension of the quantum wire and the incident optical intensity I. The obtained results show that the oscillator strength (transition life) increase (decrease) by increasing the height H. Also, the total absorption coefficient achieves a maximum value which corresponds to the energy difference of the two different electronic states and the resonant peaks shift toward the lower energies by increasing the height H.

Recently demonstrated 3D networks of Ge quantum wires in an alumina matrix, produced by a simple magnetron sputtering deposition enables the realization of nanodevices with tailored conductivity and opto-electrical properties. Their growth and ordering mechanisms as well as possibilities in the design of their structure have not been explored yet. Here, we investigate a broad range of deposition conditions leading to the formation of such quantum wire networks. The resulting structures show an extraordinary tenability of the networks&rsquo, geometrical properties. These properties are easily controllable by deposition temperature and Ge concentration. The network&rsquo, s geometry is shown to retain the same basic structure, adjusting its parameters according to Ge concentration in the material. In addition, the networks&rsquo, growth and ordering mechanisms are explained. Furthermore, optical measurements demonstrate that the presented networks show strong confinement effects controllable by their geometrical parameters. Interestingly, energy shift is the largest for the longest quantum wires, and quantum wire length is the main parameter for control of confinement. Presented results demonstrate a method to produce unique materials with designable properties by a simple self-assembled growth method and reveal a self-assembling growth mechanism of novel 3D ordered Ge nanostructures with highly designable optical properties.

Despite being known of for decades, the actual realization of memory devices based on the memristive effect is progressing slowly, due to processing requirements and the need for exotic materials which are not compatible with today’s complementary-metal-oxide-semiconductor (CMOS) technology. Here, we report an experimental study on a Ge quantum wire device featuring distinct signatures of memristive behavior favorable for integration in CMOS platform technology. Embedding the quasi-1D Ge quantum wire into an electrostatically modulated back-gated field-effect transistor, we demonstrate that individual current transport channels can be addressed directly by controlling the surface trap assisted electrostatic gating. The resulting quantization of the current represents the ultimate limit of memristors with practically zero off-state current and low footprint. In addition, the proposed device has the advantage of non-destructive successive reading cycles capability. Importantly, our findings provide a framework towards fully CMOS compatible ultra-scaled Ge based memristors.

Вивчено вплив форми поперечного перерізу квантового дроту на енергетичний спектр електронів. Проводиться розрахунок рівнів енергії електронів у квантовому дроті. Для квантового дроту AlxGa1 – xAs з нескінченною та кінцевою глибиною були отримані спектри енергетичних рівнів. Розраховано дисперсійну залежність з параболічним законом у квантовому дроті з кінцевою та нескінченною висотою потенційного бар'єру на основі Al0.25Ga0.75As та Al0.75Ga0.25As та отримано графіки дисперсійних залежностей. Результати отримано для лінійних розмірів квантового дроту в межах від 5 нм до 15 нм. Знайдено поперечні розміри циліндричних та прямокутних квантових дротів з близькими рівнями енергії. Проведено аналіз енергетичних рівнів в циліндричних та прямокутних квантових дротах та виявлено їх схожість. Показано, що рівні енергії близькі один до одного, коли площі поперечного перерізу прямокутних і циліндричних квантових дротів стають рівними. Представлено розв’язки рівняння Шредінгера, коли розв’язок для циліндричного дроту можна замінити розв’язком для прямокутного дроту. 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.

The energy of electrons and holes in cylindrical quantum wires with a finite potential well was calculated by two methods. An analytical expression is approximately determined that allows one to calculate the energy of electrons and holes at the first discrete level in a cylindrical quantum wire. The electron energy was calculated by two methods for cylindrical layers of different radius. In the calculations, the nonparabolicity of the electron energy spectrum is taken into account. The dependence of the effective masses of electrons and holes on the radius of a quantum wires is determined. An analysis is made of the dependence of the energy of electrons and holes on the internal and external radii, and it is determined that the energy of electrons and holes in cylindrical layers with a constant thickness weakly depends on the internal radius. The results were obtained for the InP/InAs heterostructures.

Based on the quantum kinetic equation for electrons, we have theoretically studied the influence of a Strong Electromagnetic Wave (EMW) on the Magneto-Thermoelectric Effects in a cylindrical quantum wire with an infinite potential (CQWIP) (for electron - optical phonon scattering) under the influence of electric field E1=(0,0,E1), magnetic field B=(0,B,0) and a strong EMW (laser radiation) E= (0,0,E0sinΩt) (where and are amplitude and frequency of EMW, respectively). We obtain the analytic expressions for the kinetic tensors sik, bik, gik, xik and the Ettingshausen coefficient (EC) in the CQWIP with the dependence on the frequency, the amplitude of EMW, the Quantum Wire (CQWIP) parameters, the magnetic field and the temperature. The results are numerically evaluated and graphed for GaAs/GaAsAl quantum wire. Then, the results in this case are compared with the case of the bulk semiconductors and others low-dimension system in order to show the difference and the novelty of the results. Moreover, we realize that as the EMW frequency increases, the EC fluctuates with a stable trend and the appearance of the Shubnikov-de Haas (SdH) oscillations pattern when we survey the dependence of EC on the magnetic field.

A two-dimensional quantum mechanical model is presented for calculating carrier transport in ultra-thin gate-all-around quantum wire transistor (GAAQWT) and carbon nanotube field effect transistor ...

In this work, the emission wavelength has been extended out to 1.3, 1.5, and 2.2 μm for InxGa1−xAs/GaAs T-shaped quantum wire (TQWR) using multi-band k.p model and variational formalism. We have investigated the impact of the indium composition on the performance of a series of TQWR through a calculation of the optical gain and transition energies. It is found that the optical gain and the emission wavelength are more influenced taking into account the effect of the indium concentration and persisted up at room temperature (RT). The results could open the way to the development of laser communication systems operating at long wavelengths and fabricated from TQWRs structure.

The current carried by a material subject to an electric field is microscopically inhomogeneous and can be modelled using scattering theory, in which electrons undergo collisions with the microscopic objects they encounter. We herein present a methodology for parameter-free calculations of the current density from first-principles using Density Functional Theory, Wannier functions and scattering matrices. The methodology is used on free-standing AB-stacked bilayer penta-silicene. This new Si allotrope has been proposed to have a higher stability than any of its hexagonal bilayer counterparts. Furthermore, its semiconducting properties make it ideal for use in electronic components. We unveil the role of the pz orbitals in the transport through a three-dimensional quantum wire and present current density streamlines that reveal the locations of the highest charge flow. The present methodology can be expanded to accommodate many electron degrees of freedom, the application of electromagnetic fields and many other physical phenomena involved in device operation., Comment: 13 pages, 12 figues, journal article

It is known that the conductance of a wire decreases linearly with the increase of its length in the macro circuit. But things are different in mesoscopic field, especially in molecular dimensional circuits due to the quantum interferences in molecular size. In this work, first principles is used to investigate how wire length and hydrogenation degree influence the conductance of molecular wires. For comparison, two types of carbon-based molecular wires, single carbon atomic wire and phenyl ring wire with single hydrogenation or dihydrogenation, are chosen and coupled to two zigzag graphene nanoribbon electrodes, respectively. We show that the conductance of zigzag carbon atomic wire with single hydrogenation exhibits an evident even-odd oscillatory behavior with the increase of wire length, while that of phenyl ring wire starts to increase before decreasing. However, when the above types of wires are edged with dihydrogenation, their conductance decreases exponentially with the increasing wire length. In addition, fine current rectification is found in asymmetric phenyl wires induced by hydrogenation degree, which can be used as diode in future molecular devices. Analyses via orbital hybridization, transmission path, HOMO-LUMO position and so on reveal the microscopic mechanism of the above interesting results.

Crystal-phase control is one of the most challenging problems in nanowire growth. We demonstrate that, in the solution-phase catalyzed growth of colloidal cadmium telluride (CdTe) quantum wires (QWs), the crystal phase can be controlled by manipulating the reaction chemistry of the Cd precursors and tri-n-octylphosphine telluride (TOPTe) to favor the production of either a CdTe solute or Te, which consequently determines the composition and (liquid or solid) state of the BixCdyTez catalyst nanoparticles. Growth of single-phase (e.g., wurtzite) QWs is achieved only from solid catalysts (y ≪ z) that enable the solution–solid–solid growth of the QWs, whereas the liquid catalysts (y ≈ z) fulfill the solution–liquid–solid growth of the polytypic QWs. Factors that affect the precursor-conversion chemistry are systematically accounted for, which are correlated with a kinetic study of the composition and state of the catalyst nanoparticles to understand the mechanism. This work reveals the role of the precursor-r...

The electronic properties of a coaxial cylindrical quantum well-barrier system constituted about an central insulating wire were determined under an external electric field. The model wire, inside to outside, was considered to be layered as A l A s / G a A s / A l x 1 G a 1 − x 1 A s / G a A s / A l x 2 G a 1 − x 2 A s . Within the framework of the effective mass-approximation, the binding energy of a hydrogenic impurity is calculated by using the combination of the fourth-order Runge-Kutta method and variational approaches. The binding energy exhibits sharp changes depending on the impurity position and the geometrical parameters of the structure such as the well widths of the G a A s wires and the height and thickness of the barrier constituted by A l x 1 G a 1 − x 1 A s . The binding energy of the electron was found to be independent from the impurity position for the specific widths of the well wires. Also, the barrier properties appeared as very effective parameters in controlling the probability distribution of the electron.

SnO 2 quantum wire/reduced graphene oxide nanocomposites (SnO 2 QW/rGO) were synthesized by a facile one-step hydrothermal method with rGO and SnCl 4 . 5H 2 O as the precursors. The SnO 2 QW/rGO nanocomposites well-dispersed in ethanol were spin-coated onto ceramics substrates to construct chemiresistive gas sensors. The H 2 S-sensing isotherm curves were obtained based on the real-time response curves of the SnO 2 QW/rGO gas sensors when operated at different temperatures ranging from 30 °C to 70 °C, from which the adsorbing/sensing performance of the specific materials were extracted and the kinetic parameters (such as response rate constant k and activation energy E a ) of the sensing-materials were quantitatively modeled. The H 2 S-sensing mechanism was found to follow Langmuir isotherm and pseudo-first-order model. Compared to pure SnO 2 QW sensors, the SnO 2 QW/rGO gas sensors exhibited higher sensitivity and faster response rate toward H 2 S, which was attributed to its lower activation energy. The SnO 2 QW/rGO gas sensors can even detect H 2 S at room temperature, highly attractive for the detection of H 2 S detection with lower power consumption.

In this paper, a theoretical study of quantum wires infrared photodetector (QRIP) under the illumination condition is presented. Here, an analytical approach is developed to calculate the average number of electrons in a quantum wire under illumination condition. Base on the presented formula, a simple mathematical formulation for the QRIP photocurrent is achieved. To show the accuracy of the model, the presented theoretical method is compared with the model reported in the previous literature. Then, QRIP photocurrent behavior over variations of the main important device parameters is investigated.

The non-linear rectification and generation of the second and third harmonic of a realistic single-electron Ga1−yAlyAs/GaAs/Ga1−xAlxAs V-groove quantum wire are calculated. The effects of the V-groove geometrical and physical parameters, such as the inter-sidewall angle, the thickness of the crescent, the position of the pinch-offs, the temperature of the sample, and the aluminum concentration on the optical coefficients are analyzed. In addition, the effect of the hydrostatic pressure and the applied external tilted static electric field on the overall configuration is determined. The results revealed that an increase in the temperature and the aluminum concentration allows fine blue-shift tuning of the coefficient peaks, while an increase of inter-sidewall angle, the thickness of the crescent, and the hydrostatic pressure allows coarse red-shift tuning. Furthermore, the polarization angle of the optic field significantly affects the peak values of the optical coefficients, while the strength of the static electric field and its orientation angle produce changes at most on the order of ~4%. The positioning of the peaks of the optical coefficients is in agreement with the calculated transition energies.

How to design silicon-based quantum wires with figure of merit ($ZT$) larger than three is under hot pursuit due to the advantage of low cost and the availability of matured fabrication technique. Quantum wires consisting of finite three dimensional quantum dot (QD) arrays coupled to electrodes are proposed to realize high efficient thermoelectric devices with optimized power factors. The transmission coefficient of 3D QD arrays can exhibit 3D, 2D, 1D and 0D topological distribution functions by tailoring the interdot coupling strengths. Such topological effects on the thermoelectric properties are revealed. The 1D topological distribution function shows the maximum power factor and the best $ZT$ value. We have demonstrated that 3D silicon QD array nanowires with diameters below $20~nm$ and length $250~nm$ show high potential to achieve $ZT\ge 3$ near room temperature., Comment: 5 pages, 6 figures

The acoustomagnetoelectric (AME) effect in an GaAs/AlGaAs rectangular quantum wire with infinite potential (RQWIP) is investigated under the influence of electromagnetic wave (EMW) by using quantum kinetic equation (QKE) method. We obtain the electron distribution function in the interaction with internal and external phonon. By solving the inhomogeneous differential equation, the current density J → and the acoustomagnetoelectric field (E AME ) are obtained in the dependence on the EMW amplitude, external acoustic wave frequency, the system temperature and the RQWIP length. The results are numerically evaluated for GaAs/AlGaAs quantum wire. We compares it to the result obtained in case of the bulk semiconductors and others low-dimension system in order to show the difference and the novelty of the results. The E AME depends non-linearly on the wire length L z and exhibits an oscillatory behavior as the function of wire length, although the stability period in long wire length condition. Moreover, we survey the impact of EMW on EAME with the dependence on the external acoustic wave frequency ω q → The result also indicates that the current density J → amplifies exponentially as the temperature increases.

Semiconductor nanowires are ideal for realizing various low-dimensional quantum devices. In particular, topological phases of matter hosting non-Abelian quasiparticles (such as anyons) can emerge when a semiconductor nanowire with strong spin-orbit coupling is brought into contact with a superconductor. To exploit the potential of non-Abelian anyons - which are key elements of topological quantum computing - fully, they need to be exchanged in a well-controlled braiding operation. Essential hardware for braiding is a network of crystalline nanowires coupled to superconducting islands. Here we demonstrate a technique for generic bottom-up synthesis of complex quantum devices with a special focus on nanowire networks with a predefined number of superconducting islands. Structural analysis confirms the high crystalline quality of the nanowire junctions, as well as an epitaxial superconductor-semiconductor interface. Quantum transport measurements of nanowire 'hashtags' reveal Aharonov-Bohm and weak-antilocalization effects, indicating a phase-coherent system with strong spin-orbit coupling. In addition, a proximity-induced hard superconducting gap (with vanishing sub-gap conductance) is demonstrated in these hybrid superconductor-semiconductor nanowires, highlighting the successful materials development necessary for a first braiding experiment. Our approach opens up new avenues for the realization of epitaxial three-dimensional quantum architectures which have the potential to become key components of various quantum devices.

Terahertz absorption in cylindrical quantum well wire under the influence of unsymmetrical electric field is investigated. The two dimensional Schrodinger equation is solved using finite difference method to obtain the eigen states and energies. The absorption spectrum is calculated using the density matrix approach. Results reveal that the absorption peaks are in the terahertz range for specific values of physical parameters. Also the results show that the frequency and amplitude of the absorption peak are completely tunable by changing the electric field and the wire diameter.

The results of studying the quantum conductance staircase of holes in one-dimensional channels obtained by the split-gate method inside silicon nanosandwiches that are the ultra-narrow quantum well confined by the delta barriers heavily doped with boron on the n-type Si (100) surface are reported. Since the silicon quantum wells studied are ultra-narrow (~2 nm) and confined by the delta barriers that consist of the negative-U dipole boron centers, the quantized conductance of one-dimensional channels is observed at relatively high temperatures ( T >77 K). Further, the current-voltage characteristic of the quantum conductance staircase is studied in relation to the kinetic energy of holes and their sheet density in the quantum wells. The results show that the quantum conductance staircase of holes in p-Si quantum wires is caused by independent contributions of the one-dimensional (1D) subbands of the heavy and light holes. In addition, the field-related inhibition of the quantum conductance staircase is demonstrated in the situation when the energy of the field-induced heating of the carriers become comparable to the energy gap between the 1D subbands. The use of the split-gate method made it possible to detect the effect of a drastic increase in the height of the quantum conductance steps when the kinetic energy of holes is increased; this effect is most profound for quantum wires of finite length, which are not described under conditions of a quantum point contact. In the concluding section of this paper we present the findings for the quantum conductance staircase of holes that is caused by the edge channels in the silicon nanosandwiches prepared within frameworks of the Hall geometry. This longitudinal quantum conductance staircase, G xx , is revealed by the voltage applied to the Hall contacts, with the plateaus and steps that bring into correlation respectively with the odd and even fractional values.

The optical absorption and the optical rectification coefficients associated to hydrogenic impurity interstate transitions in zincblende GaN-based nanostructures of the quantum wire type are investigated. The system is assumed to have cylindrical shape and the influence of external tuning probes such as hydrostatic pressure and static electric fields is particularly taken into account. The electron states are obtained within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement. The nonlinear optical coefficients are calculated using a nonperturbative solution of the density-matrix Bloch equation. Our results show that the resonance-related features of the optical response become shifted in the frequency range of the incident radiation due to the effect of the hydrostatic pressure, the strength of the applied field and the change in the impurity center position.

Organic–inorganic hybrid semiconducting nanowires have recently been widely regarded as promising candidates for electric and optical applications due to their faster carrier separation and low charge recombination. Here, we reported organic–inorganic hybrid semiconducting nanowires with photoconductive properties based on a one dimensional ABX3-type compound, (2-methylpiperidine)PbI3 (1). In 1, one dimensional infinite double chains are surrounded by protonated organic 2-methylpiperidine cations to form a quantum wire structure, which has been thought to be favorable for carrier transport. Furthermore, the prepared semiconducting nanowires of 1 display obvious photoconductive properties, which have been verified using I–V and time-dependent photoresponse measurements. All the results indicate that such semiconducting nanowires based on low dimensional organic–inorganic hybrid materials have potential photoelectric applications.

We demonstrate that, at the onset of conduction, an electrostatically defined quantum wire in bilayer graphene (BLG) with an interlayer asymmetry gap may act as a 1D semimetal, due to the multiple minivalley dispersion of its lowest subband. Formation of a non-monotonic subband coincides with a near-degeneracy between the bottom edges of the lowest two subbands in the wire spectrum, suggesting an $8e^2/h$ step at the conduction threshold, and the semimetallic behaviour of the lowest subband in the wire would be manifest as resonance transmission peaks on an $8e^2/h$ conductance plateau., 9 pages, 8 figures (including appendices)

High-mobility two-dimensional electron gas (2DEG) which resides at the interface between GaAs and AlGaAs layered semiconductors has been used experimentally and theoretically to study ballistic electron transport. The present paper is motivated by recent experiments in magnetic electron focusing. The proposed device consists of two quantum point contacts (QPCs) serving as electron injector and collector which are placed in the same semiconductor GaAs/AlGaAs heterostructure. Here we focus on a theoretical study of the injection of electrons via a quantum wire/QPC into an open two-dimensional (2D) reservoir. The transport is considered for non-interacting electrons at different transmission regimes using the mode-matching technique. The proposed mode-matching technique has been implemented numerically. Electron flow through the quantum wire with hard-wall rectangular, conical and rounded openings has been studied. We have found for these three cases that the geometry of the opening does not play a crucial role for the electron propagation. When a perpendicular magnetic field is applied the electron paths in the 2D reservoir are curved. We analyse this case both classically and quantum-mechanically. The effect of spin-splitting due to exchange interactions on the electron flow is also considered. The effect is clearly present for realistic choices of device parameters and consistent with observations. The results of this study may be applied in designing magnetic focusing devices and spin separation. Funding Agencies|Carl Trygger Science Foundation, Stockholm project [CTS 17:506]

Thermalization loss in a structure of solar cell where an intermediate band (IB) is introduced by embedding a stack of hexagonal In x Ga l-x As quantum wires (QW) in the intrinsic layer of p-i-n GaAs solar cell is calculated by a theoretical framework based on the principle of detailed balance approach. To obtain the position of IB, a finite element method is used for solving Schrodinger equation to calculate possible energy band configurations of GaAs: barrier/ In x Ga l-x As: hexagonal QW. Then, the effect of indium content of QWs, the size and period of QWs on thermalization loss is investigated. The results show that there is a fundamental limitation of ~35% for thermalization loss in achieving ultra-high efficiency QW-IBSCs.

Matters behave quite differently in the small world. Nanostructured materials, including ultrathin films (two-dimensional), quantum wire (one-dimensional), and nanoparticles-quantum dots (zero-dimensional), would have remarkable properties that are not normally observed in bulks of the same composition (three-dimensional). The reduction in the spatial dimension and confinement effects in a particular crystallographic direction within a structure tends to lead to modifications of physical properties of the system in that direction. We will generally summarize magnetic, optical, and electronic properties that are typically expected in low-dimensioned materials. Additionally, the most popular methods of synthesis as well as points that need attention when characterizing nanostructured materials will also be discussed in detail.

In the past years, various work has been devoted to improving the thermoelectric figure of merit zT, and remarkable advances have been achieved. In 2019, an abnormal zT value exceeding 400 in the Cu2Se system was measured experimentally by a Japanese group. In 1993, the theoretically predicted maximum zT value for a 0.5-nm-wide Bi2Te3 quantum wire was just 14. Sometimes, large deviations exist between experimental results and theoretical predictions. It is necessary to summarize the recent experimental results associated with the improvement of zT. In principle, the improvement of zT value arises from a high power factor and a low thermal conductivity, whereas a high power factor stems from a high Seebeck coefficient and a high electrical conductivity. Herein, several approaches were reviewed, including increasing Seebeck coefficient, electrical conductivity, power factor, and decreasing thermal conductivity to improve thermoelectric performances. In every experimental study, the underlying mechanisms, such as material components, atomic structure characterizations, and fabrication processes for enhancement of thermoelectric performances were discussed in detail. All experimental-based references have major implications for researchers in related fields. Finally, the current challenges hindering the further improvement of zT value were pointed out, and several promising routes were proposed.

In this paper, the influence of impurity parameters on the energy-dispersion spectrum of electrons and holes in a doped quantum wire with Gaussian impurity is studied. The numerical calculations have shown that the energy eigenvalues enhance, if the confinement of carriers increases. Then, the energy eigenvalues rise when the magnetic field, decay length and strength of impurity increase. Also, the type of impurity affects the energy subband structures. So that, the presence of attractive impurity reduces the energy eigenvalues, as compared to repulsive impurity. Moreover, the role of impurity parameters and the external magnetic field as a control parameter on the thermal quantities has been demonstrated in details. The results show that enhancement of magnetic field, decay length and strength of repulsive impurity decreases (increases) the entropy (internal energy) of quantum wire.