One-dimensional Electron Research Articles

Quantum Wire Coupled to Light

Experimental advances in cavity QED are raising the prospect of using light to probe quantum materials beyond the linear response regime. The capability to access quantum coherent phenomena would significantly advance the field. However, theoretical work on many-body systems coupled to light in the quantum coherent regime has been select. Here, we investigate the radiative properties of a finite-sized quantum wire in a microwave cavity. Examples of quantum wires include single-walled carbon nanotubes, a key experimental system in the field of nano-optics and plasmonics. We find that, for a variety of excited states, the repeated emission of photons results in the generation of many-body quantum entanglement. This leads to an increase in the rate at which subsequent photons are emitted, an example of Dicke superradiance. On the other hand, Pauli blocking tends to reduce this effect. Bosonization, the description of the excitations of a one-dimensional electron system as a gas of bosons, is found to be a powerful theoretical tool in this context. Its application means that many of our results generalize to wires with strong electron-electron interactions. The quantum wire thus represents a new platform to realize Dicke-model physics that does not rely on the various fine tunings necessary in traditional realizations involving many spatially isolated emitters. More broadly, this work demonstrates how quantum entanglement can be generated and measured in a many-body system. Published by the American Physical Society 2024

Dimensionally Extending from 1D MX-Chain to Ladder and Nanotube Systems: Structural and Electronic Properties.

Molecular one-dimensional (1D) electron systems have attracted much attention due to their unique electronic state, physical and chemical properties derived from high-aspect-ratio structures. Among 1D materials, mixed-valence halogen-bridged transition-metal chain complexes (MX-chains) based on coordination assemblies are currently of particular interest because their electronic properties, such as mixed-valence state and band gap, can be controlled by substituting components and varying configurations. In particular, chemistry has recently noted that dimensionally extending MX-chains through organic rung ligands can introduce and modulate electronic coupling of metal atoms between chains, i. e., interchain interactions. In this review, for the first time, we highlight the recent progress on MX systems from the viewpoint of dimensionally extending from 1D chain to ladder and nanotube, mainly involving structural design and electronic properties. Overall, dimensional extension can not only tune the electronic properties of MX-chain, but also build the unique platform for studying transport dynamics in confined space, such as proton conduction. Based on these features, we envision that the MX-chain systems provide valuable insights into deep understanding of 1D electron systems, as well as the potential applications such as nanoelectronics.

Factorized form of the dispersion relations of a traveling wave tube

The traveling tube (TWT) design in a nutshell comprises of a pencil-like electron beam (e-beam) in vacuum interacting with guiding it slow-wave structure (SWS). In our prior studies the e-beam was represented by one-dimensional electron flow and SWS was represented by a transmission line (TL). We extend in this paper our previously constructed field theory for TWTs as well the celebrated Pierce theory by replacing there the standard TL with its generalization allowing for the low frequency cutoff. Both the standard TL and generalized transmission line (GTL) feature uniformly distributed shunt capacitance and serial inductance, but the GTL in addition to that has uniformly distributed serial capacitance. We remind the reader that the standard TL represents a waveguide operating at the so-called TEM mode with no low frequency cutoff. In contrast, the GTL represents a waveguide operating at the so-called TM mode featuring the low frequency cutoff. We develop all the details of the extended TWT field theory and using a particular choice of the TWT parameters we derive a physically appealing factorized form of the TWT dispersion relations. This form has two factors that represent exactly the dispersion functions of non-interacting GTL and the e-beam. We also find that the factorized dispersion relations comes with a number of interesting features including: (i) focus points that belong to each dispersion curve as TWT principle parameter varies; (ii) formation of “hybrid” branches of the TWT dispersion curves parts of which can be traced to non-interacting GTL and the e-beam.

Influence of carrier localization on photoluminescence emission from sub-monolayer quantum dot layers

We have investigated the origins of photoluminescence from quantum dot (QD) layers prepared by alternating depositions of sub-monolayers and a few monolayers of size-mismatched species, termed as sub-monolayer (SML) epitaxy, in comparison with their Stranski–Krastanov (SK) QD counterparts. Using measured nanostructure sizes and local In-compositions from local-electrode atom probe tomography as input into self-consistent Schrödinger–Poisson simulations, we compute the 3D confinement energies, probability densities, and photoluminescence (PL) spectra for both InAs/GaAs SML- and SK-QD layers. A comparison of the computed and measured PL spectra suggests one-dimensional electron confinement, with significant 3D hole localization in the SML-QD layers that contribute to their enhanced PL efficiency in comparison to their SK-QD counterparts.

Encoding of linear kinetic plasma problems in quantum circuits via data compression

We propose an algorithm for encoding linear kinetic plasma problems in quantum circuits. The focus is on modelling electrostatic linear waves in a one-dimensional Maxwellian electron plasma. The waves are described by the linearized Vlasov–Ampère system with a spatially localized external current that drives plasma oscillations. This system is formulated as a boundary-value problem and cast in the form of a linear vector equation $\boldsymbol {A}{\boldsymbol{\psi} } = \boldsymbol {b}$ to be solved by using the quantum signal processing algorithm. The latter requires encoding of matrix $\boldsymbol {A}$ in a quantum circuit as a sub-block of a unitary matrix. We propose how to encode $\boldsymbol {A}$ in a circuit in a compressed form and discuss how the resulting circuit scales with the problem size and the desired precision.

Chaos-Assisted Dynamical Tunneling in Flat Band Superwires.

Recent theoretical investigations have revealed unconventional transport mechanisms within high Brillouin zones of two-dimensional superlattices. Electrons can navigate along channels we call superwires, gently guided without brute force confinement. Such dynamical confinement is caused by weak superlattice deflections, markedly different from the static or energetic confinement observed in traditional wave guides or one-dimensional electron wires. The quantum properties of superwires give rise to elastic dynamical tunneling, linking disjoint regions of the corresponding classical phase space, and enabling the emergence of several parallel channels. This paper provides the underlying theory and mechanisms that facilitate dynamical tunneling assisted by chaos in periodic lattices. Moreover, we show that the mechanism of dynamical tunneling can be effectively conceptualized through the lens of a paraxial approximation. Our results further reveal that superwires predominantly exist within flat bands, emerging from eigenstates that represent linear combinations of conventional degenerate Bloch states. Finally, we quantify tunneling rates across various lattice configurations and demonstrate that tunneling can be suppressed in a controlled fashion, illustrating potential implications in future nanodevices.

One-dimensional electron localization in semiconductors coupled to electromagnetic cavities

One-dimensional electron localization in semiconductors coupled to electromagnetic cavities

FRIEDEL OSCILLATIONS IN A ONE-DIMENSIONAL NON-INTERACTING ELECTRON GAS IN THE PRESENCE OF TWO IMPURITIES

Using the linear response theory, we analyze Friedel oscillations in a one-dimensional non-interacting electron gas in the presence of two impurities with different potential strengths. The impurities potentials are modelled using Dirac delta function, as well as Lorentzian and Gaussian distribution functions. Our findings show that density oscillations are strongly sensitive to both the distance between the impurities and their respective potential strengths.

Effect of ion channel guiding on the saturation mechanism of single and two-stream free-electron lasers based upon a rectangular hybrid wiggler

The paper studies a simulation of a one-dimensional nonlinear free electron laser that includes a square hybrid wiggler, prebunched electron beam, and ion-channel guiding mechanism. The Lorentz equations of motion and the Maxwell equations were combined to derive a set of non-linear differential equations solved numerically within the framework of slowly varying amplitude and wavenumber. The relativistic electron beam is assumed to be cold, and self-fields of the electron beam and the slippage of the radiation wave are ignored. The appropriate parameters are chosen in such a way that the Raman regime is being considered, where there is high density and low energy. The effect of ion-channel densities on the saturation of the device is studied for both groups Ι and ΙΙ orbits. It is found that as the ion channel density increases, the range of saturation radiation for group Ι circuits increases, too. In contrast, the saturated radiation amplitude for group ΙΙ orbits is decreased with increasing the ion-channel density. Moreover, the results of the numerical calculations show that the saturation length for an FEL with a prebunched beam is considerably shorter than that of a uniform electron beam. A free electron laser (FEL) model called the two-stream FEL, which uses two relativistic electron beams of different energy, is also studied. Comparing the radiation amplitude between FEL and TSFEL shows that TSFEL is more efficient than FEL.

Calculation of Electrophysical Characteristics of Semiconductor Quantum Wire Device Structures with One-Dimensional Electron Gas

Calculation of Electrophysical Characteristics of Semiconductor Quantum Wire Device Structures with One-Dimensional Electron Gas

Facile Synthesis of Ge@TiO2 Nanotube Hybrid Nanostructure Anode Materials for Li-Ion Batteries.

Utilizing nanostructures of Li-alloying anode materials (e.g., Si, Ge, Sn, etc.) has been proposed as a key strategy to improve the electrochemical performance. However, the main challenge lies in the costly and complex nanostructure synthesis processes. Notably, the nanostructure growth processes are mainly supported by Li-inactive templates, which later need to be removed, and the template removal process results in the destruction of the desired nanostructures. In this report, we demonstrated the use of a Li-active, self-organized TiO2 nanotube template to fabricate germanium (Ge)-based nanostructured anodes. This has been achieved as follows: first, TiO2 nanotubes are fabricated via electrochemical anodization of titanium foil. Then, the nanotubes are coated with a Ge film in the second step via electrodeposition. Besides the effective nanostructure growth using a Li-active template, the implemented electrochemical synthesis methods are cost-effective, accessible, and scalable. Furthermore, the electrochemical methods allow the fabrication of nanostructures with well-controlled structures, morphology, and compositions. Accordingly, a Ge-coated TiO2 nanotube (Ge@TiO2) nanocomposite anode has been successfully fabricated, and its electrochemical performance has been tested for Li-ion batteries. The study has shown the important roles of TiO2 nanotube arrays in improving the performance by providing strong mechanical support to buffer the volume expansion and offering a high surface area to enhance Ge-active mass loading. Moreover, the direct contact of the nanotubes with a Ti current collector facilitates one-dimensional (1D) electron transport and avoids the need of adding inactive binders or conductive additives.

The cell-centered Finite-Volume self-consistent approach for heterostructures: 1D electron gas at the Si–SiO2 interface

Achieving self-consistent convergence with the conventional effective-mass approach at ultra-low temperatures (below 4.2 K) is a challenging task, which mostly lies in the discontinuities in material properties (e.g. effective-mass, electron affinity, dielectric constant). In this article, we develop a novel self-consistent approach based on cell-centered finite-volume discretization of the Sturm–Liouville form of the effective-mass Schrödinger equation and generalized Poisson’s equation (FV-SP). We apply this approach to simulate the one-dimensional electron gas formed at the Si–SiO2 interface via a top gate. We find excellent self-consistent convergence from high to extremely low (as low as 50 mK) temperatures. We further examine the solidity of FV-SP method by changing external variables such as the electrochemical potential and the accumulative top gate voltage. Our approach allows for counting electron–electron interactions. Our results demonstrate that FV-SP approach is a powerful tool to solve effective-mass Hamiltonians.

A semiclassical approach to the magnetotransport in quasi-1D electron systems

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.

About theory of hybride TWTO and an amplifire with a complex permittivity

The purpose of this work is to construct a nonlinear theory of a hybrid between travelling wave tube (TWT) and an amplifier with a complex permittivity. Methods. The following model is considered: an ion-compensated one-dimensional electron beam penetrates the input travelling wave tube section, then flies into a medium with a complex permittivity, and then enters the output travelling wave tube section. A linear theory of this hybrid is constructed, and its results are compared with the results of the well-known linear theory of travelling wave tube. A nonlinear theory of this hybrid was constructed by a modified wave method, and the results were compared with the nonlinear travelling wave tube theory obtained by the classical Ovcharov–Solntsev’s wave method. In addition, to test the limits of applicability of the obtained results, a stationary nonlinear theory of the hybrid was constructed, obtained using the large particle method. The results of this theory were also compared with the stationary nonlinear travelling wave tube theory constructed using the large particle method. Results and conclusion. Based on the results of the developed theories, it is shown that, under certain parameters, the linear theory and nonlinear theories (both by the modified Ovcharov–Solntsev’s wave method and by the large particle method) make it possible to obtain comparable results both in the case of a classical travelling wave tube and for the hybrid under study. It is shown that under certain parameters, due to the resistive instability, the bunching of electrons can be noticeably improved and, as a result, the gain of the hybrid can exceed the gain in a classical travelling wave tube with the same parameters and the same total length of the device in the linear mode of operation. In the nonlinear mode of operation, the specified hybrid, with optimal environmental parameters, can have significantly higher values of output power and efficiency than travelling wave tube with the same value of the space charge parameter and the Pierce parameter.

3-D Computerized Ionospheric Tomography With GPS, SAR, and Ionosonde

The GPS-based computerized ionospheric tomography (CIT) has the capacity to reconstruct the three-dimensional ionosphere (i.e., electron density distribution), making it one of the most important techniques for ionospheric observation. However, the CIT technology is unable of high vertical resolution due to the restricted viewing angle. Therefore, the precision of CIT cannot be substantially enhanced with GPS only. Aiming at this issue, this paper proposes a bi-iteration algorithm that integrates GPS, Phased Array L-band Synthetic Aperture Radar on board the Advanced Land Observing Satellite (ALOS PALSAR), and ionosonde data. The key is that the joint retrieval of PALSAR and ionosonde may offer high-precision one-dimensional electron density profile along the whole path, which can effectively enhance the authenticity of the iterative initial value. The corrected initial value is then fused into the process of CIT, which can finally improve the precision of vertical resolution after two iterations. Experimental verification demonstrates that due to the ability to obtain more realistic initial values, the reconstruction accuracy of the algorithm proposed in this paper is 51.4 percent and 45.1 percent higher than the accuracy with GPS alone and with GPS and ionosonde data, respectively. This indicates that the combination of these three kinds of data can effectively improve the precision of CIT.

Ab initio study of the electronic states of V3Si in momentum space.

The electronic properties of V3Si are reported using the full-potential linearized augmented plane wave method. The electronic properties in the momentum space such as one and two dimensional electron momentum densities and the Fermi surface are presented. The momentum densities are compared with available experimental data. The one-dimensional electron momentum density i.e. the Compton profile is found to be in excellent agreement with the experiment. Anisotropy in the directional Compton profile corroborates the crystalline effects. The dimensions of the Fermi-surfaces are well captured by the 2D electron momentum density. The chemical bonding in this metallic compound is studied by means of the electron localization function and reciprocal form factor which suggest dominance of metallic bonding.

Nonpolymer Organic Solar Cells: Microscopic Phonon Control to Suppress Nonradiative Voltage Loss via Charge-Separated State.

Recent remarkable developments on nonfullerene solar cells have reached a photoelectric conversion efficiency (PCE) of 18% by tuning the band energy levels in small molecular acceptors. In this regard, understanding the impact of small donor molecules on nonpolymer solar cells is essential. Here, we systematically investigated mechanisms of solar cell performance using diketopyrrolopyrrole (DPP)-tetrabenzoporphyrin (BP) conjugates of C4-DPP-H2BP and C4-DPP-ZnBP, where C4 represents the butyl group substituted at the DPP unit as small p-type molecules, while an acceptor of [6,6]-phenyl-C61-buthylic acid methyl ester is employed. We clarified the microscopic origins of the photocarrier caused by phonon-assisted one-dimensional (1D) electron-hole dissociations at the donor-acceptor interface. Using a time-resolved electron paramagnetic resonance, we have characterized controlled charge-recombination by manipulating disorders in π-π donor stacking. This ensures carrier transport through stacking molecular conformations to suppress nonradiative voltage loss capturing specific interfacial radical pairs separated by 1.8 nm in bulk-heterojunction solar cells. We show that, while disordered lattice motions by the π-π stackings via zinc ligation are essential to enhance the entropy for charge dissociations at the interface, too much ordered crystallinity causes the backscattering phonon to reduce the open-circuit voltage by geminate charge-recombination.

As-Li electrides under high pressure: Superconductivity, plastic, and superionic states

Inorganic electrides are a new class of compounds catering to the interest of scientists due to the multiple usages exhibited by interstitial electrons in the lattice. However, the influence of the shape and distribution of interstitial electrons on physical properties and new forms of physical states is still unknown. In this work, crystal structure search algorithms are employed to explore the possibility of forming unique electrides in the As-Li system, where interstitial electrons behave as one-dimensional (1D) electron chains (1D electride) in the $Pmmm$ phase of $\mathrm{As}{\mathrm{Li}}_{7}$ and transform into zero-dimensional (0D) electron clusters (0D electride) in the $P6/mmm$ phase at 80 GPa. The $P6/mmm$ phase has relatively high superconductivity at 150 GPa $({T}_{c}=38.4\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ compared to classical electrides, even at moderate pressure with ${T}_{c}=16.6\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. In addition, a Dirac cone in the band has been observed, expanding the sources of Dirac materials. The survival of $\mathrm{As}{\mathrm{Li}}_{7}$ at room temperature is confirmed by molecular dynamics simulation at 300 K. At 1000 K, the As atoms in the system act like a solid, while a portion of the Li atoms cycle around the As atoms, and another portion of the Li atoms flow freely like a liquid, showing the unusual physical phenomenon of the coexistence of the plastic and superionic states. This suggests that the superionic and plastic states cannot only be found in hydrides but also in the electride. Our results indicate that superconducting electride $\mathrm{As}{\mathrm{Li}}_{7}$ with superionic and plastic states can exist in Earth's interior.

Simple accurate model of silicon donor arrays

Donors in silicon can now be positioned with an accuracy of about one lattice constant, making it possible to form donor arrays for quantum computation or quantum simulation applications. However, the multivalley character of the silicon conduction band combines with central cell corrections to the donor states to convert small atomic scale imperfections in donor placement into strong interdonor hybridization disorder. We present a simple model that is able to account for central cell corrections accurately, and use it to assess the impact of donor positional disorder on donor array properties in both itinerant and localized limits. Our results show that donor arrays in silicon simulate strongly disordered one-dimensional electrons.

Benzenetriimide-Based Molecular Conductor with Antiferro- to Ferromagnetic Switching Induced by Structural Change of π-stacked Array.

Benzenetriimide (BTI) is a promising building block for materials chemistry due to its characteristic 3-fold symmetry and redox properties, whereas little is known about its conductive and magnetic properties. In this study, we synthesized three charge-transfer complexes based on N,N',N''-trimethylbenzenetriimide (BTI-Me). One of the complexes contains isolated dimers of BTI-Me radical anion (BTI-Me⋅- ), while the other two have the infinite π-stacked array of BTI-Me with the formal charge of -0.5. The latter two complexes did not show metallic behavior but showed semiconducting behavior probably due to the characteristic insulation in one-dimensional electron system, so-called charge ordering and dimer-Mott insulation. The magnetic susceptibility of the complex in dimer-Mott state exhibits an unusual transition from antiferromagnetic to ferromagnetic spin states with the hysteresis loop of 15 K derived from the structural phase transition around 130 K. These properties were also supported by DFT calculations.