Vertical Field Research Articles

Strategies for Enhancing Spin-Shuttling Fidelities in Si / Si Ge Quantum Wells with Random-Alloy Disorder

Coherent coupling between distant qubits is needed for many scalable quantum computing schemes. In quantum dot systems, one proposal for long-distance coupling is to coherently transfer electron spins across a chip in a moving dot potential. Here, we use simulations to study challenges for spin shuttling in Si/SiGe heterostructures caused by the valley degree of freedom. We show that for devices with valley splitting dominated by alloy disorder, one can expect to encounter pockets of low valley splitting, given a long-enough shuttling path. At such locations, intervalley tunneling leads to dephasing of the spin wave function, substantially reducing the shuttling fidelity. We show how to mitigate this problem by modifying the heterostructure composition, or by varying the vertical electric field, the shuttling velocity, the shape and size of the dot, or the shuttling path. We further show that combinations of these strategies can reduce the shuttling infidelity by several orders of magnitude, putting shuttling fidelities sufficient for error correction within reach. Published by the American Physical Society 2024

Electromagnetically tunable spin-valley-polarized current via anomalous Nernst effect in monolayer of jacutingaite.

Monolayer jacutingaite (Pt2HgSe3) exhibits remarkable properties, including significant spin-orbit coupling and a tunable band gap, attributed to its buckled honeycomb geometry and the presence of heavy atoms. In this study, we explore the spin- and valley-dependent anomalous Nernst effect (ANE) in jacutingaite under the influence of a vertical electric field, off-resonance circularly polarized light (OCPL), and an antiferromagnetic exchange field. Our findings, within the low-energy approximation, reveal the emergence of a perfectly spin-polarized ANE with the application of appropriate OCPL and a perfectly valley-polarized ANE under an antiferromagnetic exchange field. Leveraging the robust spin-orbit coupling inherent in monolayer jacutingaite, our study highlights the potential to attain perfectly spin-valley-polarized Nernst currents across a wide range of Fermi energy levels by combining these fields in pairs with a suitable strength. The findings can be used for the development of spin-valley-based optoelectronic devices.&#xD.

Direct Collapse Accretion Disks within Dark Matter Halos: Saturation of the Magnetorotational Instability and the Field Expulsion

We have used high-resolution zoom-in simulations of direct collapse to supermassive black hole (SMBH) seeds within dark mater halos in the presence of magnetic fields generated during the collapse, down to 10−5 pc or 2 au. We confirm an efficient amplification of magnetic field during collapse, the formation of a geometrically thick self-gravitating accretion disk inside 0.1 pc, and damping of fragmentation in the disk by the field. This disk differs profoundly from SMBH accretion disks. We find the following: (1) The accretion disk is subject to the magnetorotational instability, which further amplifies the field to near equipartition. No artificial seeding of the disk field has been used. (2) The equipartition toroidal field changes its polarity in the midplane. (3) The nonlinear Parker instability develops, accompanied by the vertical buckling of the field lines, which injects material above the disk, leading to an increase in the disk scale height. (4) With the Coriolis force producing a coherent helicity above the disk, the vertical poloidal field has been generated and amplified. (5) We estimate that the associated outflow will be most probably squashed by accretion. The resulting configuration consists of a magnetized disk with β ≳ 0.1 and its magnetosphere with β ≪ 1, where β = P th/P B is the ratio of thermal to magnetic energy density. (6) The disk is highly variable, due to feeding by variable accretion flow, and strong vortical motions are present. (7) Finally, the negative gradient of the total vertical stress drives an equatorial outflow sandwiched by an inward accretion flow.

Simulation of a Mesoscale Convective System Using a New Formulation for Advection in a Bin Microphysics: Sensitivity to Advection, Microphysics, and Grid Spacing

Abstract A computationally efficient semi-Lagrangian advection (SLA) scheme designed for microphysical variable advection was implemented into the Weather Research and Forecasting (WRF) Model with spectral bin microphysics (SBM). The primary goal was to reduce the CPU time for advection of the scalar SBM variables and demonstrate its applicability to simulation of a real-data case study in the eta vertical coordinate system. A mesoscale convective system (MCS) in Midlatitude Continental Convective Clouds Experiment (MC3E-0520) was selected for simulations. We compared the SLA and high-order, nonlinear monotonic advection schemes and tested the sensitivity of the simulated radar reflectivity, microphysical, and dynamic properties of the MCS to the choice of microphysical schemes, aerosol concentration, and grid spacing. Simulations using the SLA and monotonic advection schemes were similar, and the differences between them were much smaller than those between the SBM and bulk microphysical schemes tested. Improvement of the grid resolution had a larger impact on the vertical velocity field than did the choice of aerosol concentration. The total computational time in simulations with SLA was about 25% shorter than that with monotonic advection, which resulted from a reduction of more than 50% in computational time required for advection of the microphysical variables. Significance Statement Clouds comprise particles of various sizes and types: aerosols, liquid droplets, ice crystals, hail, and snow. Two major approaches describe the time and spatial evolution of these particle species: solving basic microphysical (bin microphysics) and simplified parameterization (bulk microphysics) equations. Bin microphysics is time-consuming as it operates with size distributions described by multiple mass bins. Among the microphysical processes, the advection of the microphysical variables requires significant CPU time. We tested a new numerical advection scheme that requires several times less computer time than the standard high-order nonlinear schemes being of similar accuracy. Due to the introduced change, the advection of droplet size distributions became less of a factor affecting the total computer time of bin-type schemes. This is an important step toward making the bin approach computationally efficient without losing accuracy. It is shown that the sensitivity of the results to spatial grid spacing and to the choice of microphysical schemes is significant and may be larger than that to variations in the aerosol concentration.

Different Effects of a Super Storm on Atmospheric Electric Fields at Different Latitudes

Geomagnetic storms have a significant impact on Earth’s magnetosphere and ionosphere, as well as on the global atmospheric circuit. This study focuses on investigating the anomalous variations in the vertical atmospheric electric field at eight mid-latitude and low-latitude stations during a mega-geomagnetic storm on 24 April 2023. The majority of stations observed vertical atmospheric electric field increases, while only three nearby stations exhibited vertical atmospheric electric field decreases. The analysis revealed that vertical atmospheric electric field changes ranged from 19 to 370 V/m, and the time differences between extreme vertical atmospheric electric field values and the minimum Dst value ranged from 0 to 5.3 h. Other response patterns to this super magnetic storm at different latitudes are summarized, and the physical mechanisms of different effects of magnetic storms on the electric fields of stations at different latitudes are also discussed.

Sensitivity analysis of an inverted T-shaped vertical tunneling field effect transistor biosensor based on inserted finger type

This paper presents a biosensor based on a finger-inserted inverted T-shaped vertical tunneling field effect transistor (FP-T-TFET). In order to improve the sensitivity and performance of the biosensor, a finger-inserted contact between the source and the channel is used. A comparative analysis between the biosensor based on FP-T-TFET and conventional inverted T-shaped TFET (T-TFET) is simulated for the electrical properties and sensitivity of neutral biomolecules with different dielectric constants and charged biomolecules with different charge densities. The noise analysis of the proposed structure is also performed. Then, the effects of insertion finger distribution, cavity size and filling volume on the performance of FP-T-TFET are investigated. Finally, the structure was subjected to linear analysis, in which the pearson coefficient was 0.92, indicating that the structure has good linear correlation. The results show that the FP-T-TFET biosensor has higher sensitivity in detecting various neutral and charged biomolecules. All device simulations were performed in the TCAD environment with a well-calibrated structure.

Ground Constrained 3D Lidar SLAM Design and Implementation

Abstract. Synchronized positioning and mapping techniques based on multi-line LIDAR are mainly used for mobile platforms that require high-precision positioning, such as UAVs and self-driving cars. However, multi-line LiDAR is limited by vertical field of view and vertical angular resolution, which can affect the vertical accuracy of attitude estimation. In this paper, we aim to extract the ground information in the environment and fuse it into a factor map to constrain the vertical accuracy of the attitude. Different from the traditional geometric information-based ground plane segmentation, this paper utilizes point cloud distribution information to extract the ground cloud and uses high-confidence ground features to constrain the attitude drift by considering their distribution weights. Finally, the laser range factor, ground constraint factor and closed-loop factor are integrated under the factor graph optimization framework. The effectiveness of the method is validated on a self-constructed dataset.

Two-Dimensional Vertical Transistor with One-Dimensional van der Waals Contact.

Two-dimensional (2D) materials enable vertical field effect transistors (VFETs), which provide an alternative path for scaling down the channels of transistors. The challenge is the short channel effect when the thickness of the 2D channel decreases to ∼10 nm. Here, we show that a VFET with an ultrashort channel can be accomplished by employing a semimetal carbon nanotube (CNT) as a 1D van der Waals (vdW) contact. The CNT-VFETs with 5-10 nm MoS2 channels exhibit high on/off ratios exceeding 105, low subthreshold swing values of 160-120 mV/dec, and high current densities over 104 A/cm2. Such a switch even works with an ∼ 3.4 nm thick channel. The excellent comprehensive performance can be ascribed to the reduced short channel effect as the sub-2 nm CNT contact has weaker electrostatic screening to the gate, a reduced Fermi level pinning effect, and a highly tunable barrier. The VFETs with 1D vdW contacts hold great promise for ultrascaled transistors and are prospective in future nanoelectronics and nano-optoelectronics.

Analysis of the Meteorological Conditions and Atmospheric Numerical Simulation of an Aircraft Icing Accident

With the rapid development of the general aviation industry in China, the influence of high-impact aeronautical weather events, such as aircraft icing, on flight safety has become more and more prominent. On 1 March 2021, an aircraft conducting weather modification operations crashed over Ji’an City, due to severe icing. Using multi-source meteorological observations and atmospheric numerical simulations, we analyzed the meteorological causes of this icing accident. The results indicate that a cold front formed in northwestern China and then moved southward, which is the main weather system in the icing area. Based on the icing index, we conducted an analysis of the temperature, relative humidity, cloud liquid water path, effective particle radius, and vertical flow field, it was found that aircraft icing occurred behind the ground front, where warm-moist airflows rose along the front to result in a rapid increase of water vapor in 600–500 hPa. The increase of water vapor, in conjunction with low temperature, led to the formation of a cold stratiform cloud system. In this cloud system, there were a large number of large cloud droplets. In addition, the frontal inversion increased the atmospheric stability, allowing cloud droplets to accumulate in the low-temperature region and forming meteorological conditions conducive to icing. The Weather Research and Forecasting model was employed to provide a detailed description of the formation process of the atmospheric conditions conducive to icing, such as the uplifting motion along the front and supercooled water. Based on a real case, we investigated the formation process of icing-inducing meteorological conditions under the influence of a front in detail in this study and verified the capability of a numerical model to simulate the meteorological environment of frontal icing, in order to provide a valuable reference for meteorological early warnings and forecasts for general aviation.

Stark effect in MoSe<sub>2</sub> monolayer heterostructure

The effect of a vertical electric field on photoluminescence of a MoSe2 monolayer encapsulated with hexagonal boron nitride is investigated. In the spectra, there is a quadratic shift of the photoluminescence lines of excitons and trions from the applied potential difference, as well as a change in their intensity. It is found that the magnitude of the Stark shift significantly exceeds the theoretically predicted one. It is found that the energy distance between the trion and exciton lines in the spectra varies with the magnitude of the external field, which is due to the dependence of the density of free charge carriers in the monolayer on the field. This effect made it possible to determine the density of free charge carriers in the monolayer, which varies with the field and lies in the range from 0.3–3.4⋅1012 cm–2.

Design of spintronic devices based on adjustable half-metallicity induced by electric field in A-type antiferromagnetic bilayer NiI2

Exploring the attainment of half-metallic behavior in two-dimensional (2D) materials through external perturbations is a popular area of current research. In this work, we demonstrate, using first-principles calculations, that bilayer NiI2 (bi-NiI2) is an A-type antiferromagnetic (AFM) semiconductor with an indirect bandgap of 0.86 eV, with the most stable configuration being the AB stacking mode. Upon the application of a vertical electric field, the material transforms from its original semiconducting state into a half-metallic state. Moreover, the spin polarization reverses its orientation whenever the direction of the electric field is altered. This intriguing behavior has inspired us to design a spintronic device based on the A-type AFM bi-NiI2. By employing nonequilibrium Green's function (NEGF) combined with density functional theory (DFT) calculations, we find that the device achieves ON/OFF switching by applying vertical electric fields in parallel or anti-parallel configurations in the two leads. The device displays 100 % spin polarization in the parallel configuration (PC) scenario, driven by bias voltage or temperature differences. Utilizing either the parallel or antiparallel configuration (APC) for ON/OFF switching enables the device to exhibit tunneling magnetoresistance (TMR) of up to 1.45 × 1010 % due to bias voltage and up to 1011 % thermal TMR arising from temperature differences between the leads. These findings highlight the potential of NiI2 and A-type AFM bilayers in the design of spintronic devices.

Analysis of the underlying shield tunnel deformation caused by a newly built channel

As the development of underground space progresses, newly constructed waterways inevitably intersect with existing tunnels, posing significant challenges to the safety of underlying tunnels and making deformation control a critical issue in engineering design and construction. This study investigates the impact of waterway foundation pit excavation on the deformation of underlying tunnels. The research considers not only the vertical unloading at the bottom of the pit but also the horizontal unloading from the four side walls, which induces additional vertical stress fields in the underlying soil. These additional stresses are applied to the tunnel structure, modeled as a Pasternak elastic foundation beam, and the vertical tunnel deformation due to excavation unloading is calculated using the finite difference method. To validate the analytical results, a three-dimensional numerical model is employed. Furthermore, the study analyzes deformation trends under varying excavation sizes and the relative positions of the foundation pit and tunnel. The findings demonstrate that the proposed method provides a highly accurate, cost-effective, and efficient solution for predicting tunnel deformation during the excavation of small foundation pits. This research offers valuable insights for the design and assessment of underground structures in urban environments.

Three-dimensional analysis of multiple inclined borehole heat exchangers

This research develops and applies a numerical modelling method for inclined borehole heat exchangers (BHE) in ground-source heat pump systems. Inclined BHEs have the advantage of reducing the ground-level footprint of the overall BHE field. Computational modelling of the ground heat transfer using the commercial code COMSOL Multiphysics has revealed that inclined BHEs offer additional performance benefits compared to vertical BHE fields. When heat is injected constantly, both types of fields perform similarly at first, but over a longer period of time, the inclined BHE fields show significant benefits due to the increased ground volume in the deeper portion of the field. Similar conclusions are reached when transient loading conditions are considered. Notably, when cooling dominates, inclined BHE fields outperform vertical ones for a simulated period of 10 years. This indicates that inclined BHE fields are better equipped to handle imbalanced energy loads. To summarize, inclined BHE fields offer advantages in ground-volume utilization and resilience to energy load imbalances compared to vertical fields.

Simulation Study on Comparison of “Inside-Channel” and “On-Dielectric” Source Contact Modifications on the Performance of the Vertical Organic Field Effect Transistors

Simulation Study on Comparison of “Inside-Channel” and “On-Dielectric” Source Contact Modifications on the Performance of the Vertical Organic Field Effect Transistors

Effect of surface alignment on electric-field-induced phase transitions in blue phases

This study investigates the critical electric field thresholds required for phase transitions in the blue phases of liquid crystals (BPs) confined within vertical field switching cells. BPs are attractive for electro-optical applications due to their polarization-independent response and fast switching times; however; challenges remain regarding their limited temperature stability and previously reported high operational voltages. We employ a combined approach of polarized optical microscopy and electrical impedance analysis to identify the electric field thresholds triggering BP transitions to focal conic domains in cells with and without planar polyimide alignment layers. We show that surface alignment layers stabilize the blue phases and allow for higher applied electric fields before transitioning into the focal conic state. This suggests the possibility of a wider operational voltage range in thinner cells with alignment layers. These findings significantly improve our understanding of BPs, addressing key challenges and paving the way for their integration into advanced photonic devices, based on the CMOS technology.

A Novel Isolation Approach for GaN-Based Power Integrated Devices.

This paper introduces a novel technology for the monolithic integration of GaN-based vertical and lateral devices. This approach is groundbreaking as it facilitates the drive of high-power GaN vertical switching devices through lateral GaN HEMTs with minimal losses and enhanced stability. A significant challenge in this technology is ensuring electrical isolation between the two types of devices. We propose a new isolation method designed to prevent any degradation of the lateral transistor's performance. Specifically, high voltage applied to the drain of the vertical GaN power FinFET can adversely affect the lateral GaN HEMT's performance, leading to a shift in the threshold voltage and potentially compromising device stability and driver performance. To address this issue, we introduce a highly doped n+ GaN layer positioned between the epitaxial layers of the two devices. This approach is validated using the TCAD-Sentaurus simulator, demonstrating that the n+ GaN layer effectively blocks the vertical electric field and prevents any depletion or enhancement of the 2D electron gas (2DEG) in the lateral GaN HEMT. To our knowledge, this represents the first publication of such an innovative isolation strategy between vertical and lateral GaN devices.

Genotypic and environmental influences on colour and curcuminoids of turmeric (Curcuma longa L.) genotypes across contrasting production environments

Abstract Turmeric (Curcuma longa L.) is rich in curcuminoids, which are polyphenolic pigments make it one of the most valuable spice and medicinal plant. The rising need for natural colours and the numerous health advantages of curcuminoids are driving up the demand of turmeric. In this study, the effects of genotype and genotype × environment on the colour characteristics of 21 turmeric genotypes were examined in three different production environments namely vertical farming, greenhouse, and field conditions. The pooled analysis of variance revealed highly significant (P < 0.05) differences among genotypes (G), environments (E), and G × E interaction for three colour parameters [L* (lightness index), A* (redness index), B* (yellowness index)]. Among the genotypes, the values ranged from 41.80 to 54.76, 13.92 to 24.83 and 31.72 to 47.67 for L*, A*, B*, respectively. Erode Local (22.34), IISR Pragati (24.56) and IISR Prathiba (26.55) recorded maximum A* value under vertical farming, greenhouse, and field conditions, respectively. Correlation analysis between colour values and curcuminoids revealed a significant positive correlation (r = 0.608–0.735, P < 0.001) between A* value and curcuminoids. Furthermore, stability analysis for A* value revealed 78.87% genotype × environment interaction (GEI) from the first two principal components of GGE biplot. IISR Pragati and Waigon Turmeric are best was most stable for A* value across environments. Our study revealed that colour traits among genotypes vary widely and are strongly impacted by genetic and environmental factors. These findings are crucial for future breeding programs to enhance turmeric's colour, ensuring high-quality, stable products for producers and consumers.

Correlated insulators and charge density wave states in chirally twisted triple bilayer graphene

Motivated by recent experimental observations of displacement-field-tuned correlated insulators at integer and half-integer fillings in chirally twisted triple bilayer graphene (CTTBG) [Phys.Rev.Lett.132.246501], we study the single-particle and interacting physics of CTTBG. We find that there are two inequivalent stacking orders, i.e., AB-AB-BC and AB-AB-AB, and both exhibit flat bands with nontrivial topology. We then use the Hartree–Fock approximation to calculate the rich phase diagram of CTTBG at all integer and half-integer fillings in both stacking orders and under the vertical displacement field. Under a small displacement field, the groundstates are flavor polarized states for AB-AB-BC stacking order and intervalley coherent states for AB-AB-AB stacking order at all integer and half-integer fillings. A larger displacement field will turn them into layer-polarized states. At half-integer fillings, the groundstates also exhibit charge density wave (CDW) order. For AB-AB-AB stacking, the groundstates at half-integer fillings are always 2 × 1 stripe state among a range of displacement fields. For AB-AB-BC stacking, the groundstates at half-integer fillings are also 2 × 1 stripe states under a small displacement field and a larger displacement will possibly favor further translation-symmetry-breaking, depending on filling and the direction of the displacement field. We demonstrate that the CDW states observed in the experiment can originate from the strong Coulomb interaction of the flat band electrons.

Electrical contact property and control effects for stable T(H)-TaS2/C3B metal-semiconductor heterojunctions.

Metal-semiconductor heterojunctions are the basis for developing new electronic devices. Here, T(H)-TaS2/C3B metal-semiconductor heterostructures are constructed by different phase T- and H-TaS2 monolayers combined with the C3B monolayer. The calculated corrected binding energies, phonon band structures, elastic constants, and molecular dynamics simulations indicated that both heterojunctions are highly stable, meaning that T(H)-TaS2/C3B heterojunctions possibly exist in experiments. The electronic property calculations showed that the intrinsic T(H)-TaS2/C3B heterojunction is an n(p)-type Schottky contact with a low Schottky barrier height (SBH), which is very important for the design of high-performance field-effect transistors. The electronic properties of the T(H)-TaS2/C3B heterojunctions can be controlled by varying the vertical strain and external electric field; however, the strain only resulted in a small change in the heterojunction SBH. Nevertheless, under external electrical field control, the T-TaS2/C3B heterojunction could manage a transition from an n-type Schottky contact to an n-type Ohmic contact and the H-TaS2/C3B heterojunction could be altered from a p-type Schottky contact to a p-type Ohmic contact. These findings provide theoretical insights into the electronic and electrical contact properties of the T(H)-TaS2/C3B heterojunction, which could be beneficial for developing n-type MOS and p-type MOS transistors.

Large-scale sub-5-nm vertical transistors by van der Waals integration

Vertical field effect transistor (VFET), in which the semiconductor is sandwiched between source/drain electrodes and the channel length is simply determined by the semiconductor thickness, has demonstrated promising potential for short channel devices. However, despite extensive efforts over the past decade, scalable methods to fabricate ultra-short channel VFETs remain challenging. Here, we demonstrate a layer-by-layer transfer process of large-scale indium gallium zinc oxide (IGZO) semiconductor arrays and metal electrodes, and realize large-scale VFETs with ultra-short channel length and high device performance. Within this process, the oxide semiconductor could be pre-deposited on a sacrificial wafer, and then physically released and sandwiched between metals, maintaining the intrinsic properties of ultra-scaled vertical channel. Based on this lamination process, we realize 2 inch-scale VFETs with channel length down to 4 nm, on-current over 800 A/cm2, and highest on-off ratio up to 2 × 105, which is over two orders of magnitude higher compared to control samples without laminating process. Our study not only represents the optimization of VFETs performance and scalability at the same time, but also offers a method of transfer large-scale oxide arrays, providing interesting implication for ultra-thin vertical devices.