Chiral Vector Research Articles

Possibility of the magnitude of the chiral vector having an effect on the terahertz radiation generation by hot electrons in zigzag carbon nanotubes driven by DC-AC fields

The possibility that the magnitude of a chiral or circumferential vector (Chv) influences the generation of terahertz radiations (T-rays) by hot electrons in zigzag carbon nanotubes (z-CNTs) driven by direct current (DC) and alternating current (AC) fields is taken into consideration. The study conducted a semiclassical theoretical analysis by using the Boltzmann kinetic equation to determine current density in relation to high AC field frequency (ω) and z-CNT circumference (|Chv|) when hot electrons were present. A numerical analysis was performed by varying the magnitude of the circumference of the tube at a fixed temperature and the strong hot electron injection rate at a predetermined value. When the circumference of the semiconducting zigzag carbon nanotubes (sz-CNTs) is increased, the current density's lowest and highest peaks are also enhanced (i.e., large amplitudes). This increases positive differential conductivity (PDC), necessitating enhanced domain suppression for higher potential generation of T-rays. In contrast, it was observed that reducing the tube's circumference in metallic zigzag carbon nanotubes (mz-CNTs) resulted in an increase in both the lowest and highest peaks of current density, which enhanced the PDC. These findings imply that larger circumferential sz-CNTs and smaller circumferential mz-CNTs may be more suitable candidates for a higher potential generation of T-rays with applications pertinent to modern science and technology.

Ferroelectricity Induced by a Combination of Crystallographic Chirality and Axial Vector.

Ferroelectric materials compatible with magnetism and/or conductive properties provide a platform for exploring unconventional phenomena, such as the magnetoelectric effect, nonreciprocal responses, and nontrivial superconductivity. Though recent studies on multiferroics have offered several approaches, the search for magnetic and/or conducting ferroelectric materials is still a challenging issue under the traditional "d0-ness" rule, refusing active d electrons. Here, we propose the emergence of ferroelectricity through a combination of crystallographic chirality and axial vector, accepting even non-d0 magnetic ions. This proposal is demonstrated in quasi-one-dimensional magnetic systems SrM2V2O8 (M = Ni, Mg, and Co). The ferroelectric phase transition is observed by measurements of neutron powder diffraction and dielectric properties in all compositions. Structural analyses and first-principles calculations indicate that these magnetic compounds are identified as proper-type ferroelectrics whose ferroelectric phase transition is achieved by spiral motions of crystallographic screw chains formed by edge-shared MO6 octahedra, considered as the combination of locally defined chirality and axial vector. Computationally predicted magnitude of spontaneous polarization of SrM2V2O8 reaches ∼100 μC/cm2, comparable to that of conventional ferroelectrics, despite the incorporation of non-d0 magnetic elements. The mechanism proposed in this study offers a unique approach to the exploration of new ferroelectrics beyond the traditional paradigms.

Water structures in tip-charged carbon nanotubes.

Carbon nanotubes (CNTs) have potential applications in separation membranes and nanofluidic devices. It is well known that the behavior of water molecules confined in CNTs is affected by surface functional groups and external electric fields, leading to structural changes. The understanding of these structural changes of water within various CNTs is crucial, particularly in the context of material separation. While there have been many investigations into the effects of individual specific functional groups, a comprehensive understanding of the effect of these functional groups and the electric fields they generate on water molecules remains elusive. In this study, we investigate the properties of water molecules in tip-charged CNTs of (8,8), (10,10), and (12,12) chiral vectors with positive charges at one tip and negative charges at the other tip. Abstraction of ionized functional groups as tip charges enables a comprehensive understanding that is independent of individual functional groups. The symmetrically arranged tip-charges spontaneously generate a strong and symmetric electric field in the CNTs. However, the strength and directionality of the electric field are non-uniform and complex. In the interiors of (8,8) and (10,10) tip-charged CNTs, helical and square structures, which have disturbances caused by the non-uniformity of the electric field, are observed. The properties of the water molecules differed significantly in the center of the CNTs and near positive and negative charges, despite the electric field symmetry. In (12,12) tip-charged CNTs with 12 charges, a local ring structure is observed in the vicinity of negative charges but not in the vicinity of positive charges. It is concluded that the water structures in tip-charged CNTs have different characteristics from those in plain CNTs under a uniform electric field.

Supersymmetric States in Anti-de Sitter D=3 Supergravity with Chiral Torsion.

In this Letter, we construct a supersymmetric model, obtained by deforming N=2 anti-de Sitter D=3 supergravity through a chiral vector component of the torsion. Moreover, we study the existence of supersymmetric states of such theory by inspecting the presence of Killing spinors on a specific bosonic solution.

A Novel CNFET SRAM-Based Compute-In-Memory for BNN Considering Chirality and Nanotubes

As AI models grow in complexity to enhance accuracy, supporting hardware encounters challenges such as heightened power consumption and diminished processing speed due to high throughput demands. Compute-in-memory (CIM) technology emerges as a promising solution. Furthermore, carbon nanotube field-effect transistors (CNFETs) show significant potential in bolstering CIM technology. Despite advancements in silicon semiconductor technology, CNFETs pose as formidable competitors, offering advantages in reliability, performance, and power efficiency. This is particularly pertinent given the ongoing challenges posed by the reduction in silicon feature size. We proposed an ultra-low-power architecture leveraging CNFETs for Binary Neural Networks (BNNs), featuring an advanced state-of-the-art 8T SRAM bit cell and CNFET model to optimize performance in intricate AI computations. Through meticulous optimization, we fine-tune the CNFET model by adjusting tube counts and chiral vectors, as well as optimizing transistor ratios for SRAM transistors and nanotube diameters. SPICE simulation in 32 nm CNFET technology facilitates the determination of optimal transistor ratios and chiral vectors across various nanotube diameters under a 0.9 V supply voltage. Comparative analysis with conventional FinFET-based CIM structures underscores the superior performance of our CNFET SRAM-based CIM design, boasting a 99% reduction in power consumption and a 91.2% decrease in delay compared to state-of-the-art designs.

Cove-Edged Chiral Graphene Nanoribbons with Chirality-Dependent Bandgap and Carrier Mobility.

Graphene nanoribbons (GNRs) have garnered significant interest due to their highly customizable physicochemical properties and potential utility in nanoelectronics. Besides controlling widths and edge structures, the inclusion of chirality in GNRs brings another dimension for fine-tuning their optoelectronic properties, but related studies remain elusive owing to the absence of feasible synthetic strategies. Here, we demonstrate a novel class of cove-edged chiral GNRs (CcGNRs) with a tunable chiral vector (n,m). Notably, the bandgap and effective mass of (n,2)-CcGNR show a distinct positive correlation with the increasing value of n, as indicated by theory. Within this GNR family, two representative members, namely, (4,2)-CcGNR and (6,2)-CcGNR, are successfully synthesized. Both CcGNRs exhibit prominently curved geometries arising from the incorporated [4]helicene motifs along their peripheries, as also evidenced by the single-crystal structures of the two respective model compounds (1 and 2). The chemical identities and optoelectronic properties of (4,2)- and (6,2)-CcGNRs are comprehensively investigated via a combination of IR, Raman, solid-state NMR, UV-vis, and THz spectroscopies as well as theoretical calculations. In line with theoretical expectation, the obtained (6,2)-CcGNR possesses a low optical bandgap of 1.37 eV along with charge carrier mobility of ∼8 cm2 V-1 s-1, whereas (4,2)-CcGNR exhibits a narrower bandgap of 1.26 eV with increased mobility of ∼14 cm2 V-1 s-1. This work opens up a new avenue to precisely engineer the bandgap and carrier mobility of GNRs by manipulating their chiral vector.

Generating Mathematical Expressions for Estimation of Atomic Coordinates of Carbon Nanotubes Using Genetic Programming Symbolic Regression

The study addresses the formidable challenge of calculating atomic coordinates for carbon nanotubes (CNTs) using density functional theory (DFT), a process that can endure for days. To tackle this issue, the research leverages the Genetic Programming Symbolic Regression (GPSR) method on a publicly available dataset. The primary aim is to assess if the resulting Mathematical Equations (MEs) from GPSR can accurately estimate calculated atomic coordinates obtained through DFT. Given the numerous hyperparameters in GPSR, a Random Hyperparameter Value Search (RHVS) method is devised to pinpoint the optimal combination of hyperparameter values, maximizing estimation accuracy. Two distinct approaches are considered. The first involves applying GPSR to estimate calculated coordinates (uc, vc, wc) using all input variables (initial atomic coordinates u, v, w, and integers n, m specifying the chiral vector). The second approach applies GPSR to estimate each calculated atomic coordinate using integers n and m alongside the corresponding initial atomic coordinates. This results in the creation of six different dataset variations. The GPSR algorithm undergoes training via a 5-fold cross-validation process. The evaluation metrics include the coefficient of determination (R2), mean absolute error (MAE), root mean squared error (RMSE), and the depth and length of generated MEs. The findings from this approach demonstrate that GPSR can effectively estimate CNT atomic coordinates with high accuracy, as indicated by an impressive R2≈1.0. This study not only contributes to the advancement of accurate estimation techniques for atomic coordinates but also introduces a systematic approach for optimizing hyperparameters in GPSR, showcasing its potential for broader applications in materials science and computational chemistry.

Evaluating the elastic behaviour of boron nitride nanotube (BNNT) reinforced phenolic nanocomposites

The present analysis concerns investigation of the elastic behavior of boron nitride nanotube (BNNT)-reinforced phenolic nanocomposite using molecular dynamics (MD) simulations. In the investigation, an armchair BNNT with chiral vectors (10, 10) was used as reinforcement and novolac-type phenolic chains and formaldehyde mixture was used as a matrix. The crosslinking of phenolic chains and formaldehyde mixture was achieved to obtain the three-dimensional crosslinked structure reinforced with BNNT. In addition to the tensile elastic modulus, the glass transition temperature was evaluated for the bulk phenolic resin and the nanocomposite using the density-temperature relationship. Based on the results, it was concluded that 6.8% (volume fraction) of BNNT can enhance the elastic modulus of the composite by ∼15 times. Poisson’s ratio was found to be independent of the mixing ratio. It was also observed that reinforcement with BNNT can enhance the glass transition temperature of the nanocomposite. Continuum-based rule of mixture showed a good correlation with the MD predictions.

Chiral Mechanical Effect of the Tightly Focused Chiral Vector Vortex Fields Interacting with Particles.

The coupling of the spin-orbit angular momentum of photons in a focused spatial region can enhance the localized optical field's chirality. In this paper, a scheme for producing a superchiral optical field in a 4π microscopic system is presented by tightly focusing two counter-propagating spiral wavefronts. We calculate the optical forces and torques exerted on a chiral dipole by the chiral light field and reveal the chiral forces by combining the light field and dipoles. Results indicate that, in addition to the general optical force, particles' motion would be affected by a chiral force that is directly related to the particle chirality. This chiral mechanical effect experienced by the electromagnetic dipoles excited on a chiral particle could be characterized by the behaviors of chirality density and flux, which are, respectively, associated with the reactive and dissipative components of the chiral forces. This work facilitates the advancement of optical separation and manipulation techniques for chiral particles.

The Coleman correspondence at the free fermion point

We prove that the truncated correlation functions of the charge and gradient fields associated with the massless sine-Gordon model on \mathbb{R}^2 with \beta=4\pi exist for all coupling constants and are equal to those of the chiral densities and vector current of free massive Dirac fermions. This is an instance of Coleman's prediction that the massless sine-Gordon model and the massive Thirring model are equivalent (in the above sense of correlation functions). Our main novelty is that we prove this correspondence starting from the Euclidean path integral in the nonperturbative regime of the infinite volume models. We use this correspondence to show that the correlation functions of the massless sine-Gordon model with \beta=4\pi decay exponentially and that the corresponding probabilistic field is localized.

Controlled Hierarchical Self-Assembly of Nanoparticles and Chiral Molecules into Tubular Nanocomposites.

In this work, we show how the kinetics of molecular self-assembly can be coupled with the kinetics of the colloidal self-assembly of inorganic nanoparticles, which in turn drives the formation of several distinct hierarchically assembled tubular nanocomposites with lengths over tens of micrometers. These colloidal nanoparticles primarily serve as "artificial histones," around which the as-assembled supramolecular fibrils are wound into deeply kinetically trapped single-layered nanotubes, which leads to the formation of tubular nanocomposites that are resistant to supramolecular transformation thermally. Alternatively, when these nanoparticles are aggregated prior to the event of molecular self-assembly, these as-formed nanoparticle "oligomers" would be encapsulated into the thermodynamically favored double-layer supramolecular nanotubes, which enables the non-close-packing of nanoparticles inside the nanotubes and results in the nanoparticle superlattices with an open channel. Furthermore, increasing the amounts of nanoparticles enables the assembly of nanoparticles into pseudohexagonal superlattices at the external surface in a sequential fashion, which ultimately drives the formation of triple-layered hierarchically assembled tubular nanocomposites. Importantly, the sense of helicity transfers from the supramolecular nanotubes to the pseudo nanoparticle superlattices with a chiral vector of (2, 9). Our findings represent a strategy for controlling the hierarchical assembly bridging supramolecular chemistry to the inorganic solids to realize the complexity by design.

Voltage over‐scaling CNT‐based 8‐bit multiplier by high‐efficient GDI‐based counters

A new low-power and high-speed multiplier is presented based on the voltage over scaling (VOS) technique and new 5:3 and 7:3 counter cells. The VOS reduces power consumption in digital circuits, but different voltage levels of the VOS increase the delay in different stages of a multiplier. Hence, the proposed counters are implemented by the gate-diffusion input technique to solve the speed limitation of the VOS-based circuits. The proposed GDI-based 5:3 and 7:3 counters save power and reduce the area by 2x and 2.5x, respectively. To prevent the threshold voltage (Vth) drop in the suggested GDI-based circuits, carbon nanotube field-effect transistor (CNTFET) technology is used. In the counters, the chirality vector and tubes of the CNTFETs are properly adjusted to attain full-swing outputs with high driving capability. Also, their validation against heat distribution under different time intervals, as a major issue in the CNTFET technology is investigated, and their very low sensitivity is confirmed. The low complexity, high stability and efficient performance of the presented counter cells introduce the proposed VOS-CNTFET-GDI-based multiplier as an alternative to the previous designs.

Design of Ternary Logic Circuits using Pseudo N-type CNTFETs

In this paper, a novel method is presented to design ternary logic circuits for nanoelectronics applications. The ternary logic is a best alternative to the binary logic because it offers reduced interconnects, faster operating speed and reduced chip area. The digital logic circuit designs are developed using Pseudo N-type carbon nanotube field effect transistors (CNTFETs). The threshold voltage of CNTFETs is altered by the CNT diameter that is defined by the chirality vector. The ternary inverters such as standard inverter (SI), positive inverter (PI) and negative inverter (NI) and ternary basic gates such as AND, NAND, OR and NOR gates are designed. Furthermore, the half adder circuits developed which assists to develop complex circuit schematics. The proposed ternary schematics are designed and simulated using the HSPICE simulator. Moreover, the performance of the proposed circuits are investigated in terms of delay, power dissipation and power delay product (PDP) and compared with the existing circuits. It is observed that the proposed circuits show average performance improvement up to 47.48% over the existing circuits.

Reasonable BN nanotubes composed of B–B and N–N bonds: A theoretical prediction

What kinds of the nanotubes rolled from the rectangular di-BN are indeed reasonable? In order to clarify this question, two types of mathematically and physically rigorous boron nitride nanotubes (di-BNNTs) along the (n,0) and (0,n) chiral vectors, composed of diboron B−−B and azo N−−N bonds, are investigated with the aid of density functional theory (DFT) simulations. Firstly, there is no chiral nanotube with (n,m) at all by considering its 1D periodicity. Secondly, the phonon dispersion relations clearly support the lattice dynamic stabilities of the thinnest zigzag (6,0) and armchair (0,4) di-BNNTs with the radii of 2.385 Å and 2.911 Å, respectively. The ab-initio molecular dynamics (AIMD) simulations further confirm their thermodynamic stabilities at least at 1000 K. Furthermore, the energetic, mechanical, and electronic features of these two kinds of di-BNNTs are systematically studied. According to our calculations, di-BNNTs possess excellent mechanical strengths and adjustable band gaps, which endow them the promising application potential in solar conversion field.

Low power design of explicit‐pulsed dual‐edge‐triggered level‐converting flip‐flop based on carbon nanotubes field‐effect transistors

Power consumption and performance are the two main concerns in designing pulse-triggered level-converting flip-flops (LCFF). In this letter, through the research on the level conversion circuits, an explicit-pulsed dual-edge triggered LCFF based on the carbon nanotubes field-effect transistors (CNTFETs) is proposed by using the multi-source voltage technology. The proposed flip-flop increases the speed by reducing the number of transistors in the charge/discharge path. The characteristics of the CNTFETs are used to obtain transistors with different threshold voltages by changing the chiral vector to optimize the circuit structure and further reduce the power consumption. In addition, the power consumption is further reduced due to the small on-current of the CNTFETs. The proposed novel structure is simulated in HSPICE using the Stanford model. Simulation results indicate that our proposed flip-flop reduces 62.9% to 72.4% of power consumption and 73.6% to 89.1% of delay in comparison with other flip-flops proposed in the references at 50% data switching activity.

A High-Frequency Multi-Mode Universal Filter for GHz Applications in CNFET Technology

This paper presents a new circuit structure of a multi-mode active filter, using only 16 transistors and 2 grounded capacitors in carbon nanotube field-effect transistor (CNFET) technology which is biased at [Formula: see text][Formula: see text]V supply. The proposed multi-input, single-output (MISO) filter has the capability of working as low-pass, band-pass, high-pass, band-stop and all-pass filters in all the operating modes (voltage, current, transconductance and transresistance). In addition, the quality factor ([Formula: see text]) parameter can be tuned electronically independent of the center frequency ([Formula: see text]). The HSPICE simulation results show that the proposed filter consumes only 971[Formula: see text][Formula: see text]W at 1[Formula: see text]GHz center frequency, assuming [Formula: see text][Formula: see text]pF and the nanotube pitch parameter of ([Formula: see text] nm) and the chiral vector of (22,0), while the number of nanotubes is considered as [Formula: see text] for all the transistors. Moreover, the main circuit performances such as the center frequency and the power consumption of the circuit vary by 5.4% and 11.6%, respectively, for the standard temperature variation.

General double monodromy inflation

We revisit the roller-coaster cosmology based on multiple stages of monodromy inflation. Working within the framework of effective flux monodromy field theory, we include the full range of strong coupling corrections to the inflaton sector. We find that flattened potentials $V\ensuremath{\sim}{\ensuremath{\phi}}^{p}+\ensuremath{\cdots}$ with $p\ensuremath{\lesssim}1/2$, limited to $N\ensuremath{\lesssim}25\ensuremath{-}40$ $e$-folds in the first stage of inflation, continue to fit the cosmic microwave background. They yield $0.96\ensuremath{\lesssim}{n}_{s}\ensuremath{\lesssim}0.97$ and produce relic gravity waves with $0.006\ensuremath{\lesssim}r\ensuremath{\lesssim}0.035$, in full agreement with the most recent bounds from BICEP/Keck. The nonlinear derivative corrections generated by strong dynamics in effective field theory (EFT) also lead to equilateral non-Gaussianity ${f}_{\mathrm{NL}}^{\mathrm{eq}}\ensuremath{\simeq}\mathcal{O}(1)\ensuremath{-}\mathcal{O}(10)$, close to the current observational bounds. Finally, in the multistage roller coaster, an inflaton--hidden sector $U(1)$ coupling can produce a tachyonic chiral vector background, which converts rapidly into tensors during the short interruption by matter domination. The produced stochastic gravity waves are chiral, and so they may be clearly identifiable by gravity wave instruments like LISA, Big Bang Observer, Einstein Telescope, NANOgrav, or SKA, depending on the precise model realization. We also point out that the current attempts to resolve the ${H}_{0}$ tension using early dark energy generically raise ${n}_{s}$. This might significantly alter the impact of BICEP/Keck data on models of inflation.

Structure refinement, microstrains and crystallite sizes of Mg-Ni-phyllosilicate nanoscroll powders

The morphology and structure of (Ni x Mg1−x )3Si2O5(OH)4 synthetic phyllosilicate nanoscrolls have been studied by means of electron microscopy and X-ray powder diffraction. Scrolling of phyllosilicate layers originates from size differences between octahedral and tetrahedral sheets. This strain-energy-driven process raises a number of questions, including the preferred direction of scrolling (along the a or b axis) and the presence of residual microstrain. In order to clarify these points, the structure of (Ni x Mg1−x )3Si2O5(OH)4 phyllosilicates (x = 0, 0.33, 0.5, 0.67, 1) was first described by a monoclinic Cc (9) unit cell, whose parameters decrease with increasing Ni concentration. The Williamson–Hall plots constructed for x = 0 and 0.67 reveal the absence of microstrain, which suggests that scrolling is an effective means of stress relaxation. The sizes of the crystallites were determined by using Rietveld refinement with predefined needle-like models and fundamental parameter fitting with crystallites of arbitrary form. Both approaches show qualitative and quantitative correlation, in terms of aspect ratio, with electron microscopy data. At the same time, the phyllosilicates studied do not demonstrate one preferred direction of scrolling: instead, there might be a mixture of chirality vectors codirected with the a or b axis, with the proportion altering with Ni concentration.

Photoinduced 120-degree spin order in the Kondo-lattice model on a triangular lattice

We theoretically predict the emergence of 120-degree spin order as a nonequilibrium steady state in the photodriven Kondo-lattice model on a triangular lattice. In the system away from the half filling with ferromagnetic ground state, the photoexcitation of conduction electrons and the photoinduced renormalization of bandwidth cause reconstruction of the band structure and subsequent redistribution of the electrons through relaxations, which result in an electronic structure similar to that in the half-filled system at equilibrium, where the 120-degree spin order is stabilized. In this photoinduced 120-degree spin ordered phase, domains of different spin-ordered planes are formed, and vortices of spin chirality vectors called ${Z}_{2}$ vortices appear at points where multiple domains meet. We also discuss favorable conditions and experimental feasibility to observe the predicted photoinduced magnetic phase transition by investigating dependencies on the light parameters (amplitude, frequency, and polarization), the electron filling, the strength of Kondo coupling, and the effects of antiferromagnetic coupling among the localized spins. Photoinduced magnetic structures proposed so far have been limited to simple collinear (anti)ferromagnetic orders or local magnetic defects in magnets. The present work paves a way to the optical creation of complex noncollinear magnetisms as a global nonequilibrium steady phase in photodriven systems.

Thermodynamics and correlations featured quantum criticality of transverse-field Ising model with off-diagonal exchange interactions

We study the quantum phase transitions (QPTs) and quantum criticality of transverse-field Ising model with off-diagonal exchange interactions. In the absence of magnetic field, the clockwise spiral (CWS), counterclockwise spiral (CCWS) and longitudinal ferromagnetic (xFM) phases are revealed by the spin chirality vector κz and longitudinal spin–spin correlation Cxx mutually. The general QPT is diagnosed by the temperature power-law divergence of Grüneisen ratio (GR) Γ∼±T−1. The critical scaling is further done to capture the quantum critical point (QCP) by analyzing κz and specific heat, which offers a direct access to distill the critical exponents (δ, β, α) that fulfill the Essam–Fisher relation α+β(1+δ)=2, providing a new clue to detect the general QPT. Subsequently, some scaling hypothesis equations are proposed to check the scaling analysis. In a magnetic field, an additional field-induced transverse ferromagnetic (zFM) phase is unveiled. Specifically, for the xFM phase transition into zFM one, the transverse-field Ising terms predominates, which approximately keeps the Z2 symmetry at hc=1, giving rise to the self-dual quantum criticality, demonstrated by the constant of GR irrelevant of temperature. Furthermore, the gapped and gapless low-lying excitations of quantum phases are manifested by the thermal Drude weight and specific heat.