Search

The self-energy in Born approximation including exchange of interacting one-dimensional systems is expressed in terms of a single integral about the potential which allows a fast and precise calculation for any potential analytically. The imaginary part of the self-energy as damping of single-particle excitations shows a rich structure of different areas limited by single-particle and collective excitation lines. The corresponding spectral function reveals a pseudogap, a splitting of excitations into holons and antiholons as well as bound states. [ABSTRACT FROM AUTHOR]

Copyright of German International Journal of Modern Science / Deutsche Internationale Zeitschrift für Zeitgenössische Wissenschaft is the property of Artmedia24 and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, we use NEGF quantum transport simulations to study the fundamental detection limit of ultra-scaled Si nanowire FET (NWT) biosensors. A N-doped NWT is found to be more sensitive for negatively charged analytes as explained by the nature of the detection mechanism. Our results predict threshold voltage shifts due to a single-charge analyte of tens to hundreds of mV in air or low-ionic solutions. However, with typical ionic solutions and SAM conditions, the sensitivity rapidly drops to the mV/q range. Our results are then extended to the detection of a single 20-base-long DNA molecule in solution. The impact of front- and/or back-gate biasing on the sensitivity and limit of detection is studied and a signal-to-noise ratio of 10 is predicted. Opportunities and challenges to reach down to single-analyte detection in such systems are also discussed, including the ionic and oxide-solution interface-charge screening and ways to recover unscreened sensitivities. [ABSTRACT FROM AUTHOR]

It is well known that the laser diode performance will inevitably deteriorate when the device is heated. It has been a difficult issue to solve to date. In this letter, we are reporting a new solution to improve high-temperature performance of the laser diodes. The device uses a kind of directly-coupled well-wire hybrid quantum confinement (HQC) structure of the active medium based on the InGaAs–GaAs–GaAsP material system. This special HQC structure is constructed based on the strain-driven indium (In)-segregation effect and the growth orientation-dependent on-GaAs multi-atomic step effect. The measurement and analysis for the HQC laser sample show that the carrier leakage loss, the Auger recombination and gain-peak shifting due to heating are reduced in the HQC structure. It therefore increases the optical gain for lasing at high temperature. The power conversion efficiency is enhanced by >57% and the threshold carrier density drops by >24% at T ⩾ 360 K, in comparison to the traditional quantum-well laser performance. A higher characteristic temperature of 240 K is obtained as well. It implies the better thermal stability of the HQC laser structure. These achievements show a significant prospect for developing high thermo-optic performance of laser diodes. [ABSTRACT FROM AUTHOR]

The issue of the magnetotransport in any quasi one-dimensional (quasi-1D) electron system has not hoarded so much attention as the magnetotransport in two-dimensional (2D) system. At most, at the beginning of the realization of those systems, some experimental studies and phenomenological models were developed. However, it is an interesting subject that can throw light on the physical mechanisms determining the transport properties of low-dimensional electron systems. In our previous paper, Hidalgo (Eur Phys J Plus 137:1–-14, 2022), we described in detail a semiclassical global approach to the quantum Hall and Shubnikov-de Haas phenomena in a 2D system for both, the integer and fractional quantum Hall effects (IQHE and FQHE), and not only in semiconductors quantum wells but also in graphene. Here, we focus on the magnetotransport in a quasi-1D electron system following also a semiclassical approach, i.e., taking into consideration the Landau-type density of states for such system and its implication in the conductivity. [ABSTRACT FROM AUTHOR]

Novel nanoscale probes are opening new venues for understanding unconventional electronic and magnetic functionalities driven by multiscale lattice complexity in doped high-temperature superconducting perovskites. In this work, we focus on the multiscale texture at supramolecular level of oxygen interstitial (O-i) atomic stripes in HgBa2CuO4+y at optimal doping for the highest superconducting critical temperature (TC) of 94 K. We report compelling evidence for the nematic phase of oxygen interstitial O-i atomic wires with fractal-like spatial distribution over multiple scales using scanning micro- and nano-X-ray diffraction. The scale-free distribution of O-i atomic wires at optimum doping extending from the micron down to the nanoscale has been associated with the intricate filamentary network of hole-rich metallic wires in the CuO2 plane. The observed critical opalescence provides evidence for the proximity to a critical point that controls the emergence of high-temperature superconductivity at optimum doping. [ABSTRACT FROM AUTHOR]

Beyond the state-of-the-art Cd-containing quantum wires (QWs), heavy-metal-free semiconductor QWs, such as ZnSe, are of great interest for next-generation environmental-benign applications. Unfortunately, simultaneous, on-demand manipulation of their radial and axial sizes—that allows strong quantum confinement in the blue-light region—has so far been challenging. Here we present a two-step catalyzed growth strategy that enables independent, high-precision and wide-range controls over the diameter and length of ZnSe QWs. We find that a new epitaxial orientation between the cubic-phase Ag2Se solid catalyst and wurtzite ZnSe QWs kinetically favors the formation of defect-free ultrathin QWs. Thanks to their high uniformity, the resulting blue-light-active, phase-pure ZnSe QWs exhibit well-defined excitonic absorption with the 1Se–1Sh transition linewidth as narrow as sub-13 nm. Combining the transient absorption spectroscopy, we further show that surface electron traps in these ZnSe QWs can be eliminated by thiol passivation, which results in long-lived charge carriers and high-efficiency solar-to-hydrogen conversion. [ABSTRACT FROM AUTHOR]

For the 1D Hubbard model with spin-orbit coupling and proximity-induced s-wave superconductivity, the damping rates of quasiparticles are studied in the framework of density-matrix renormalization group (DMRG) approach. It is shown that low-energy excitations belonging to the Hubbard bands are stable against strong electron interaction at the spin-polarized regime. In order to confirm this result analytically, the low-energy model of the strongly interacting spin-polarized nanowire was derived in the second order of perturbation theory. This model generalizes Kitaev chain, taking into account the hoppings and anomalous pairings in the secondary coordination spheres as well as terms describing charge correlations. The amplitudes of the latter ones are small, and the system can be effectively described by quadratic Hamiltonian supporting stable Majorana excitations, which confirms numerical calculations. The topological phase diagram of effective model is studied in the framework of mean-field approximation. The evolution of topological phase boundaries under increasing of charge correlations is studied, and the important role of the joint realization of different types of interactions is noted. The results obtained can be applied when describing the Al-EuS-InAs hybrid system, recently synthesized and studied in searching for Majorana bound states. [ABSTRACT FROM AUTHOR]

In this study, we use NEGF quantum transport simulations to study the fundamental detection limit of ultra-scaled Si nanowire FET (NWT) biosensors. A N-doped NWT is found to be more sensitive for negatively charged analytes as explained by the nature of the detection mechanism. Our results predict threshold voltage shifts due to a single-charge analyte of tens to hundreds of mV in air or low-ionic solutions. However, with typical ionic solutions and SAM conditions, the sensitivity rapidly drops to the mV/q range. Our results are then extended to the detection of a single 20-base-long DNA molecule in solution. The impact of front- and/or back-gate biasing on the sensitivity and limit of detection is studied and a signal-to-noise ratio of 10 is predicted. Opportunities and challenges to reach down to single-analyte detection in such systems are also discussed, including the ionic and oxide-solution interface-charge screening and ways to recover unscreened sensitivities.

Perovskite materials, celebrated for their exceptional optoelectronic properties, have seen extensive application in the field of light-emitting diodes (LEDs), where research is as abundant as the proverbial "carloads of books." In this review, the research of perovskite materials is delved into from a dimensional perspective, with a focus on the exemplary performance of low-dimensional perovskite materials in LEDs. This discussion predominantly revolves around perovskite quantum wires and perovskite nanorods. Perovskite quantum wires are versatile in their growth, compatible with both solution-based and vapor-phase growth, and can be deposited over large areas-even on spherical substrates-to achieve commendable electroluminescence (EL). Perovskite nanorods, on the other hand, boast a suite of superior characteristics, such as polarization properties and tunability of the transition dipole moment, endowing them with the great potential to enhance light extraction efficiency. Furthermore, zero-dimensional (0D) perovskite materials like nanocrystals (NCs) are also the subject of widespread research and application. This review reflects on and synthesizes the unique qualities of the aforementioned materials while exploring their vital roles in the development of high-efficiency perovskite LEDs (PeLEDs)., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

As the condensed matter analog of Majorana fermion, the Majorana zero-mode is well known as a building block of fault-tolerant topological quantum computing. This review focuses on the recent progress of Majorana experiments, especially experiments about semiconductor-superconductor hybrid devices. We first sketch Majorana zero-mode formation from a bottom-up view, which is more suitable for beginners and experimentalists. Then, we survey the status of zero-energy state signatures reported recently, from zero-energy conductance peaks, the oscillations, the quantization, and the interactions with extra degrees of freedom. We also give prospects of future experiments for advancing one-dimensional semiconductor nanowire-superconductor hybrid materials and devices. [ABSTRACT FROM AUTHOR]

Novel nanoscale probes are opening new venues for understanding unconventional electronic and magnetic functionalities driven by multiscale lattice complexity in doped high-temperature superconducting perovskites. In this work, we focus on the multiscale texture at supramolecular level of oxygen interstitial (O-i) atomic stripes in HgBa2CuO4+y at optimal doping for the highest superconducting critical temperature (TC) of 94 K. We report compelling evidence for the nematic phase of oxygen interstitial O-i atomic wires with fractal-like spatial distribution over multiple scales using scanning micro- and nano-X-ray diffraction. The scale-free distribution of O-i atomic wires at optimum doping extending from the micron down to the nanoscale has been associated with the intricate filamentary network of hole-rich metallic wires in the CuO2 plane. The observed critical opalescence provides evidence for the proximity to a critical point that controls the emergence of high-temperature superconductivity at optimum doping.

This article examines the role of field strength, frequency, and many-body scattering during the ultrafast optoelectronic response in a direct-gap semiconductor nanowire using numerical simulation. Following resonant laser excitation, an AC or bias DC field perturbs the 1D e-h plasma as it relaxes by carrier-phonon and Coulomb scattering. For bias DC fields, the laser-excited carrier distributions evolve to a static non-equilibrium from which a stable DC mobility is calculated. Carrier-phonon collisions contain the e-h carriers near energy minima for fields of 0.5 kV/cm or less, while the Coulomb collisions redistribute some electrons across the Brillouin zone where they drift into other band structure energy minima and are there contained by phonon scattering. This behavior results in carrier mobilities with a field-strength dependence specific to a 1D solid. For AC probe fields, the analyze the resulting frequency-dependent conductivity for frequencies between the plasmon frequency and interband resonance. In all cases, we compare results to standard-conductivity models by calculating distribution-averaged collision rates and times, and show how, unlike in the bulk, these quantities for the nanowire are strongly dependent on both field magnitude and frequency. • Characterizes band structure dependence of optoelectronic response in nanowires. • Calculates the nonlinear DC-field dependence of quantum wire carrier mobility. • Calculates the frequency dependent quantum wire optical conductivity. • Characterizes the relative influence of many-body collisions in these calculations. • Explores how AC and DC results deviate from established models in bulk solids. [ABSTRACT FROM AUTHOR]

Using a tight-binding mode-space NEGF technique, we explore the essential physics, design and performance potential of the III-V core-shell (CS) nanowire (NW) heterojunction tunneling field-effect transistor (TFET). The CS TFET “line-tunneling” current increases significantly with the core diameter dC and outperforms the best III-V axial “point-tunneling” NW heterojunction TFET ION by up to 6× for dC = 6.6 nm. Reaching such a high level of current at low supply voltage, however, requires and involves specific and sometime unanticipated optimizations and physics that are thoroughly investigated here. In spite of the commonly accepted view, we also show and explain the weak gate-length dependency observed for the line-tunneling current in a III-V TFET. We further investigate the effect of electron-phonon scattering and discrete dopant impurity band tails on optimized CS NW TFETs. Including those non-idealities, the CS-TFET inverter performance significantly outperforms that of the axial TFETs. The low-power (LP) VDD = 0.35V CS-inverter delay is comparable to that of the high-performance (HP) Si CMOS using VDD = 0.55, which shows promise for an LP TFET technology with HP speed.

In this work, the finite-difference time domain (FDTD) has been employed to calculate the energy levels and wave functions of a three-dimensional (3D) cylindrical quantum wire. The inside of the wire is at zero potential, and the background medium is 4.6 eV. This is a true 3D procedure based on a direct implementation of the time-dependent Schrödinger equation. Here, the dependence on the pressure and the temperature of the electronic effective mass is used. We study the effects temperature and pressure simultaneously on the entropy and the specific heat of the system using the Tsallis formalism. The results show that (i) the specific heat obtained by Tsallis has a peak structure. (ii) The entropy has almost the same values at very low temperatures with different pressures. (iii) The peak value of the specific heat with enhancing the pressure shifts toward lower temperatures. (iv) The peak value of the specific heat and its position depend on the value of the entropic index q. [ABSTRACT FROM AUTHOR]

A theoretical investigation has been made of the magnetoplasmon excitations in a quasi-one-dimensional electron system composed of vertically stacked, self-assembled InAs/GaAs quantum dots. The smaller length scales involved in the experiments impel us to consider a perfectly periodic system of two-dimensionally confined InAs quantum dot layers separated by GaAs spacers. Subsequent system is subjected to a two-dimensional confining (harmonic) potential in the x – y plane and an applied magnetic field (B) in the symmetric gauge. This scheme defines virtually a system of quantum wire comprised of vertically stacked quantum dots (VSQD). We derive and discuss the Dyson equation, the generalized (nonlocal and dynamic) dielectric function, and the inverse dielectric function for investigating the single-particle and collective (magnetoplasmon) excitations within the framework of (full) random-phase approximation (RPA). As an application, we study the influence of the confinement potential and the magnetic field on the component eigenfunctions, the density of states (DOS), the Fermi energy, the collective excitations, and the inverse dielectric functions. How the B-dependence of DOS validate the VSQD mimicking the realistic quantum wires, the Fermi energy oscillates as a function of the Bloch vector, the intersubband single-particle continuum bifurcates at the origin, a collective excitation emerges and propagates within the gap of the split single-particle continuum, and the alteration in the well- and barrier-widths allows to customize the excitation spectrum in the desired energy range are some of the remarkable features of this investigation. These findings demonstrate, for the very first time, the significance of investigating the system of VSQD subjected to a quantizing magnetic field. Given the edge over the planar quantum dots and the foreseen applications in the single-electron devices and quantum computation, investigating the system of VSQD is deemed vital. The results suggest exploiting magnetoplasmon qubits to be a potential option for implementing the solemn idea of quantum state transfer in devising quantum gates for the quantum computation and quantum communication networks. [ABSTRACT FROM AUTHOR]

• A flexible hybrid photodiode was constructed on a PET substrate. • The deep location of LUMO level of PC71BM below the InP QWs results in the separation of the charge carriers. • The flexible hybrid diode exhibits photosensitivity exceeds 10-fold compared to InP QWs. • The flexible hybrid photodiode showed high photo-stability and reproducibility. Flexible photodiodes have become a focus of current research because they may offer unique applications in various new areas requiring lightweight, flexible, and mechano‐resistive features. In this study, InP quantum wires have been prepared via microwave approach with a mean diameter of 7 nm. The morphology and elemental composition of the prepared InP quantum wires were characterized using the scanning electron microscope (SEM), the energy dispersive X-ray spectroscopy (EDS), the transmission electron microscopy (TEM), and the selected area of electron diffraction (SAED). The crystal structure was studied using the X-ray diffractometer (XRD). The crystallite size and the lattice strain were estimated using the size-strain model. The Raman scattering spectroscopy and photoluminescence measurements reveal the strong quantum confinement of the InP QW. A flexible hybrid InP QW/PC71BM heterostructure photodiode was constructed on a PET substrate. The developed photodiode exhibits high photoresponsivity and fast detection of incident laser photons. The charge transport mechanism based on the band-offset alignment diagram was discussed. [ABSTRACT FROM AUTHOR]

Self-assembled ErSi2-x nanowires were grown on Si(001) substrates with average nanowire width of 2.8 nm. Submonolayer coverage of platinum was deposited postgrowth. Scanning tunneling microscopy showed that platinum preferentially deposited on the nanowire surface versus the Si surface. Reactive ion etching of ErSi2-x nanowires with and without platinum on the surface demonstrated that platinum acted as a more resistant etch mask. Etching platinum coated nanowires with lower platinum coverage produced linear arrays of quantum dots with a diameter of approximately the pre-etched nanowire width. The platinum layer was shown to passivate the highly reactive rare earth disilicide surface. ©2004 IEEE.

Chiral edge states of (2 + 1) -dimensional Abelian and non-Abelian topological phases can be represented by chiral conformal field theories with integer and noninteger values of central charge, respectively. In this work we describe certain edge states in terms of constrained fermionic fields that realize chiral coset CFT structures. This construction arises naturally in the so-called quantum wires approach for topological phases and allows for representing fractionalized edge states directly in terms of fermionic degrees of freedom. At the same time, the constrained fermions description introduces some subtleties concerning gauge anomalies since it involves the coupling of chiral fermions to gauge fields. We describe in this paper how to handle these issues. [ABSTRACT FROM AUTHOR]

Abstract Between many prominent contributions of Markus Büttiker to mesoscopic physics, the scattering theory approach to the electron transport and noise stands out for its elegance, simplicity, universality, and popularity between theorists working in this field. It offers an efficient way to theoretically investigate open electron systems far from equilibrium. However, this method is limited to situations where interactions between electrons can be ignored, or considered perturbatively. Fortunately, this is the case in a broad class of metallic systems, which are commonly described by the Fermi liquid theory. Yet, there exist another broad class of electron systems of reduced dimensionality, the so-called Tomonaga–Luttinger liquids, where interactions are effectively strong and cannot be neglected even at low energies. Nevertheless, strong interactions can be accounted exactly using the bosonization technique, which utilizes the free-bosonic character of collective excitations in these systems. In the present work, we use this fact in order to develop the scattering theory approach to the bosonization of open quasi-one dimensional electron systems far from equilibrium. Highlights • The scattering theory for bosons and application to bosonization. • Strong interactions considered non-perturbatively. • Dissipation effect in electrical circuits. [ABSTRACT FROM AUTHOR]

We study charge transport in the Peierls-Harper model with a quasi-periodic cosine potential. We compute the Landauer-type conductance of the wire. Our numerical results show the following: (i) When the Fermi energy lies in the absolutely continuous spectrum that is realized in the regime of the weak coupling, the conductance is quantized to the universal conductance. (ii) For the regime of localization that is realized for the strong coupling, the conductance is always vanishing irrespective of the value of the Fermi energy. Unfortunately, we cannot make a definite conclusion about the case with the critical coupling. We also compute the conductance of the Thue-Morse model. Although the potential of the model is not quasi-periodic, the energy spectrum is known to be a Cantor set with zero Lebesgue measure. Our numerical results for the Thue-Morse model also show the quantization of the conductance at many locations of the Fermi energy, except for the trivial localization regime. Besides, for the rest of the values of the Fermi energy, the conductance shows a similar behavior to that of the Peierls-Harper model with the critical coupling. [ABSTRACT FROM AUTHOR]

Quantum wires occupy a unique status among the semiconducting nanostructures with reduced dimensionality, no other system seems to have engaged researchers with as many appealing features to pursue. This paper aims at a core issue related with the magnetoplasmon excitations in the quantum wires characterized by the confining harmonic potential and subjected to a longitudinal electric field and a perpendicular magnetic field in the symmetric gauge. Despite the substantive complexity, we obtain the exact analytical expressions for the eigenfunction and eigenenergy, using the scheme of ladder operators, which fundamentally characterize the quantal system. Crucial to this inquiry is an intersubband collective excitation that evolves into a magnetoroton — above a threshold value of magnetic field — which observes a negative group velocity between the maxon and the roton. The evidence of negative group velocity implies anomalous dispersion in a gain medium with the population inversion that forms the basis for the lasing action of lasers. Thus, the technological pathway that unfolds is the route to devices exploiting the magnetoroton features for designing the novel optical amplifiers at nanoscale and hence paving the way to a new generation of lasers. [ABSTRACT FROM AUTHOR]