Atoms In Electric Fields Research Articles

Shortwave Ultrahigh-Sensitivity Rydberg Atomic Electric Field Sensing Based on a Subminiature Resonator

Shortwave Ultrahigh-Sensitivity Rydberg Atomic Electric Field Sensing Based on a Subminiature Resonator

Electrochemical Switching of Electromagnetism by Hierarchical Disorder Tailored Atomic Scale Polarization.

High-frequency electronic response governs a broad spectrum of electromagnetic applications from radiation protection, and signal compatibility, to energy recovery. Despite various efforts to manage electric conductivity, dynamic control over dielectric polarization for real-time electromagnetic modulation remains a notable challenge. Herein, an electrochemical lithiation-driven hierarchical disordering strategy is demonstrated for actively modulating electromagnetic properties. The controllable formation and diffusion of coherent interfaces and cation vacancies tailor the coupling of atomic electric field and thus the locally polarized domains, which leads to the reversible electromagnetic transparency/absorption switching with a tunable range of -0.8--20.4 dB for the reflection loss and a broad operation bandwidth of 4.6 GHz. Compared to traditional methods of heteroatomic doping, hydrogenation, mechanical deformation, and phase transition, the electrochemical strategy shows a larger regulation scope of dielectric permittivity with the maximum increase ratios of 260% and 1950% for real and imaginary parts, respectively. This enables the construction of various device architectures including the adaptive window and pixelated metasurface. The results offer opportunities to achieve intelligent electromagnetic devices and pave an avenue to rejuvenate various electromagnetic functions of semiconductive oxides.

DFT-Assisted Investigation of the Electric Field and Charge Density Distribution of Pristine and Defective 2D WSe2 by Differential Phase Contrast Imaging.

Most properties of solid materials are defined by their internal electric field and charge density distributions which so far are difficult to measure with high spatial resolution. Especially for 2D materials, the atomic electric fields influence the optoelectronic properties. In this study, the atomic-scale electric field and charge density distribution of WSe2 bi- and trilayers are revealed using an emerging microscopy technique, differential phase contrast (DPC) imaging in scanning transmission electron microscopy (STEM). For pristine material, a higher positive charge density located at the selenium atomic columns compared to the tungsten atomic columns is obtained and tentatively explained by a coherent scattering effect. Furthermore, the change in the electric field distribution induced by a missing selenium atomic column is investigated. A characteristic electric field distribution in the vicinity of the defect with locally reduced magnitudes compared to the pristine lattice is observed. This effect is accompanied by a considerable inward relaxation of the surrounding lattice, which according to first principles DFT calculation is fully compatible with a missing column of Se atoms. This shows that DPC imaging, as an electric field sensitive technique, provides additional and remarkable information to the otherwise only structural analysis obtained with conventional STEM imaging.

Rational Design of Dynamic Interface Water Evolution on Turing Electrocatalyst toward the Industrial Hydrogen Production.

Manipulating the structural and kinetic dissociation processes of water at the catalyst-electrolyte interface is vital for alkaline hydrogen evolution reactions (HER) at industrial current density. This is seldom actualized due to the intricacies of the electrochemical reaction interface. Herein, this work introduces a rapid, nonequilibrium cooling technique for synthesizing ternary Turing catalysts with short-range ordered structures (denoted as FeNiRu/C). These advanced structures empower the FeNiRu/C to exhibit excellent HER performance in 1 m KOH with an ultralow overpotential of 6.5 and 166.2 mV at 10 and 1000 mA cm-2, respectively, and a specific activity 7.3 times higher than that of Pt/C. Comprehensive mechanistic analyses reveal that abundant atomic species form asymmetric atomic electric fields on the catalyst surface inducing a directed evolution and the dissociation process of interfacial H2O molecules. In addition, the locally topologized structure effectively mitigates the high hydrogen coverage of the active site induced by the high current density. The establishment of the relationship between free water population and HER activity provides a new paradigm for the design of industrially relevant high performance alkaline HER catalysts.

GaN atomic electric fields from a segmented STEM detector: Experiment and simulation.

Atomic electric fields in a thin GaN sample are measured with the centre-of-mass approach in 4D-scanning transmission electron microscopy (4D-STEM) using a 12-segmented STEM detector in a Spectra 300 microscope. The electric fields, charge density and potential are compared to simulations and an experimental measurement using a pixelated 4D-STEM detector. The segmented detector benefits from a high recording speed, which enables measurements at low radiation doses. However, there is measurement uncertainty due to the limited number of segments analysed in thisstudy.

Direct observation of strong surface reconstruction in partially reduced nickelate films

The polarity of a surface can affect the electronic and structural properties of oxide thin films through electrostatic effects. Understanding the mechanism behind these effects requires knowledge of the atomic structure and electrostatic characteristics at the surface. In this study, we use annular bright-field imaging to investigate the surface structure of a Pr0.8Sr0.2NiO2+x (0 < x < 1) film. We observe a polar distortion coupled with octahedral rotations in a fully oxidized Pr0.8Sr0.2NiO3 sample, and a stronger polar distortion in a partially reduced sample. Its spatial depth extent is about three unit cells from the surface. Additionally, we use four-dimensional scanning transmission electron microscopy (4D-STEM) to directly image the local atomic electric field surrounding Ni atoms near the surface and discover distinct valence variations of Ni atoms, which are confirmed by atomic-resolution electron energy-loss spectroscopy (EELS). Our results suggest that the strong surface reconstruction in the reduced sample is closely related to the formation of oxygen vacancies from topochemical reduction. These findings provide insights into the understanding and evolution of surface polarity at the atomic level.

Moiré Superlattice Structure of Pleated Trilayer Graphene Imaged by 4D Scanning Transmission Electron Microscopy.

Moiré superlattices in graphene arise from rotational twists in stacked 2D layers, leading to specific band structures, charge density and interlayer electron and excitonic interactions. The periodicities in bilayer graphene moiré lattices are given by a simple moiré basis vector that describes periodic oscillations in atomic density. The addition of a third layer to form trilayer graphene generates a moiré lattice comprised of multiple harmonics that do not occur in bilayer systems, leading to nontrivial crystal symmetries. Here, we use atomic resolution 4D-scanning transmission electron microscopy to study atomic structure in bilayer and trilayer graphene moiré superlattices and use 4D-STEM to map the electric fields to show subtle variations in the long-range moiré patterns. We show that monolayer graphene folded into an S-bend graphene pleat produces trilayer moiré superlattices with both small (<2°) and larger twist angles (7-30°). Annular in-plane electric field concentrations are detected in high angle bilayers due to overlapping rotated graphene hexagons in each layer. The presence of a third low angle twisted layer in S-bend trilayer graphene, introduces a long-range modulation of the atomic structure so that no real space unit cell is detected. By directly imaging trilayer moiré harmonics that span from picoscale to nanoscale using 4D-STEM, we gain insights into the complex spatial distributions of atomic density and electric fields in trilayer twisted layered materials.

Ultrathin graphdiyne oxide-intercalated MXene: A new heterostructure with interfacial synergistic effect for high performance lithium-ion storage

Two-dimensional (2D) layered heterostructures demonstrate strong interfacial synergistic effect, promote ion transfer and accelerate electrochemical reaction kinetics, and have great development potential in the field of energy storage. Here, ultra-thin 2D graphdiyne oxide (GDYO) was successfully prepared and creatively used as an intercalator to form a sandwich-like heterostructure with MXene (Ti3C2Tx) through electrostatic self-assembly. Intercalation of GDYO effectively extends the interlayer spacing of Ti3C2Tx nanosheets and meanwhile generates atomic interfacial electric fields within the heterostructure, leading to desirable pseudocapacitive behaviors and superior lithium-ion migration kinetics. Theoretical and experimental data reveal that the electrochemical performance of the heterostructure is superior to that of pure Ti3C2Tx or GDYO nanosheets when utilized as anodes for lithium-ion storage. A reversible capacity of ≈490.0 mAh g−1 at 2.0 A g−1 is attained by the Ti3C2Tx/GDYO-5 wt% heterostructure (≈770.0 mAh g−1 at 0.1 A g−1) with a long cycle life of 489.2 mAh g−1 after 1000 cycles.

Atomic microwave electric field detection enhanced by a loading resonator.

Accurate detection technology of the microwave electric field is an important foundation to explore new materials, devices, and electromagnetic effects. In this paper, the design of a microwave electric field detection enhanced by a resonant cavity was proposed and experimentally verified. The simulation results show that the enhancement factor is 3.45 at the position of 3 mm from the square SRR). By combining the experimental system, the actual enhancement factor is 3.31(6), and the corresponding electric field detection sensitivity is increased from 1.02 V/m to 0.30 V/m. The proposed scheme provides certain technical support for the weak microwave electric field detection and the development of the integrated atomic microwave detection unit.

Towards the interpretation of a shift of the central beam in nano-beam electron diffraction as a change in mean inner potential

The measurement of electric fields in scanning transmission electron microscopy (STEM) is a highly investigated field of research. The constant improvement of spatial resolution in STEM and the development of new hardware for the fast acquisition of diffraction patterns even paved the way for the measurement of atomic electric fields. Although the basic principle that an electric field leads to a tilt of the focussed electron probe that can be detected as a shift of the diffraction pattern in the back focal plane of the objective lens seems quite simple, many challenges arose in the measurement of fields in a quantitative way. In the present study we investigate whether a shift of the diffraction pattern that occurs at an interface between two materials can be related to the electric field which is caused by the difference of the mean inner potentials of the two materials. To this end, experiments and simulations are compared. It is demonstrated that the difference in mean inner potential has an influence on the observed effect, but a quantitative interpretation is difficult. The influence of image recording effects such as shot noise and the modulation transfer function are investigated as well as further effects such as e.g. sample tilt. In addition, the influence of the observed effect on a strain measurement is shown.

Accelerated Ionic and Charge Transfer through Atomic Interfacial Electric Fields for Superior Sodium Storage.

Atomic interfacial electric fields hold great potential for boosting ionic and charge transfer and accelerating electrochemical reaction kinetics. Here, built-in electric fields within the heterostructure are created by electrostatic assembly of unilamellar titano-niobate/graphene (reduced graphene oxide) nanosheets as building blocks. Scanning Kelvin probe microscopy confirms the existence of built-in electric fields by detecting the unbalanced surface potential of disparate nanosheets in the heterostructure, which facilitates ion and electron transfer, thus enabling an excellent reversible sodium storage capacity of 245 mAh g-1 at 0.05 A g-1. Theoretical analysis also confirms that the electric field can enhance the electric conductivity and facilitate electron transfer at the atomic interface. Moreover, in situ TEM observations confirm the homogeneous intercalation of sodium ions and very small volume expansion of the hybrid materials. As a result, a highly stable lifetime of 3000 cycles is achieved with capacity retention of 98.8%. This work attests the importance of accelerating ionic and charge transfer through atomic interfacial electric field for superior sodium storage.

External sources in a minimal and nonminimal CPT-odd Lorentz violating Maxwell electrodynamics

This paper is devoted to the study of interactions between stationary electromagnetic sources for the minimal and nonminimal CPT-odd photon sector of the Standard Model Extension (SME), where we search mainly for physical phenomena not present in the Maxwell electrodynamics. First, we consider the minimal CPT-odd sector, where the Lorentz violation is caused by the Carroll–Field–Jackiw (CFJ) term, namely, [Formula: see text], and we treat the Lorentz breaking parameter [Formula: see text] perturbatively up to second order. We consider effects due to the presence of point-like charges, Dirac strings and point-like dipoles. In special, we calculate the electromagnetic field produced outside the string and investigate the so-called Aharonov–Bohm bound states in Lorentz violation context. Afterwards, we consider a model where the Lorentz violation is generated by the higher-derivative version of the CFJ model, namely, [Formula: see text], which is a dimension five term of the CPT-odd sector of the nonminimal SME. For this higher-derivative model, we obtain effects up to second order in [Formula: see text] related to the presence of point-like charges and a steady current line. We use overestimated constraints for the Lorentz violation parameters in order to investigate the physical relevance of some results found in atomic systems. We also make an overestimate for the background vectors using experimental data from the atomic electric field.

Real-space visualization of intrinsic magnetic fields of an antiferromagnet.

Characterizing magnetic structures down to atomic dimensions is central to the design and control of nanoscale magnetism in materials and devices. However, real-space visualization of magnetic fields at such dimensions has been extremely challenging. In recent years, atomic-resolution differential phase contrast scanning transmission electron microscopy (DPC STEM)1 has enabled direct imaging of electric field distribution even inside single atoms2. Here we show real-space visualization of magnetic field distribution inside antiferromagnetic haematite (α-Fe2O3) using atomic-resolution DPC STEM in a magnetic-field-free environment3. After removing the phase-shift component due to atomic electric fields and improving the signal-to-noise ratio by unit-cell averaging, real-space visualization of the intrinsic magnetic fields in α-Fe2O3 is realized. These results open a new possibility for real-space characterization of many magnetic structures.

Computation of Phonon Density of States, Atomic Electrostatic Potential and Electric Field Gradient Tensor Using Single Crystal Data of Six Benzene Sulfonamide Based Compounds

Molecular dynamic study of benzene sulfonamide based compounds was carried out to compute several properties like phonon density of states, atomic electric potential and electric field gradient tensor components and then compared. This work establishes the correlation between physical properties and the quantity of carbon atoms in a molecule. The GULP program was used to do all the calculations and reported single crystal data.

Atomic Electrostatic Maps of Point Defects in MoS2.

In this study, we use differential phase contrast images obtained by scanning transmission electron microscopy combined with computer simulations to map the atomic electrostatic fields of MoS2 monolayers and investigate the effect of sulfur monovacancies and divancancies on the atomic electric field and total charge distribution. A significant redistribution of the electric field in the regions containing defects is observed, with a progressive decrease in the strength of the projected electric field for each sulfur atom removed from its position. The electric field strength at the sulfur monovacancy sites is reduced by approximately 50% and nearly vanishes at the divacancy sites, where it drops to around 15% of the original value, demonstrating the tendency of these defects to attract positively charged ions or particles. In addition, the absence of the sulfur atoms leads to an inversion in the polarity of the total charge distribution in these regions.

Direct Atomic-Scale Structure and Electric Field Imaging of Triazine-Based Crystalline Carbon Nitride.

Crystalline carbon nitrides (CNs) have recently attracted considerable attention owing to their superior photocatalytic activity. However, the electron-beam-sensitive nature of crystalline CNs hinders atomic-resolution imaging of their local structures by conventional (scanning) transmission electron microscopy ((S)TEM) techniques. Here, the atomic structure of a triazine-based crystalline CN, poly(triazine imide) (PTI) incorporated with lithium and chloride ions, is unambiguously revealed using the emerging imaging technique of differential phase contrast STEM under a low dose. The lightest-element Li/H configuration is resolved within framework cavities of PTI and significantly affects the electronic structure for photoabsorption. The atomic electric field of PTI crystal directly determined in real space provides a fundamental evidence for the chemical bonding of Li ions and adjacent atoms for the migration of photogenerated carriers. These results facilitate the comprehension on local atomic configuration and chemical bonding state of crystalline CNs and can lead to a deeper understanding of the photocatalytic mechanism.

Rydberg Atom Electric Field Sensors for Communications and Sensing

Rydberg atom electric field sensors are projected to enable novel capabilities for resilient communications and sensing. This quantum sensor is small-size, highly sensitive, and broadly tunable, and it has the potential for performing precision vector electric field and angle-of-arrival measurements. While these atomic electric field sensors will not replace traditional receivers in commodity applications for RF signal reception, these sensors could be an enabling technology in niche application spaces. This review outlines the principles of operation of atomic electric field sensors and compares their performance capabilities to traditional RF receivers. It also highlights recent research and development efforts in atomic electric field sensing and identifies applications for which these sensors are projected to impact communications and remote sensing.

Shift of the first ionization threshold of Sm atom in electric field

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed

Surface States Enhanced Dynamic Schottky Diode Generator with Extremely High Power Density Over 1000 W m-2.

The overloaded energy cost has become the main concern of the now fast developing society, which make novel energy devices with high power density of critical importance to the sustainable development of human society. Herein, a dynamic Schottky diode based generator with ultrahigh power density of 1262.0 W m−2 for sliding Fe tip on rough p‐type silicon is reported. Intriguingly, the increased surface states after rough treatment lead to an extremely enhanced current density up to 2.7 × 105 A m−2, as the charged surface states can effectively accelerate the carriers through large atomic electric field, while the reflecting directions are regulated by the built‐in electric field of the Schottky barrier. This research provides an open avenue for utilizing the surface states in semiconductors in a subversive way, which can co‐utilize the atomic electric field and built‐in electric field to harvest energy from the mechanical movements, especially for achieving an ultrahigh current density power source.

Atomic 2D electric field imaging of a Yagi–Uda antenna near-field using a portable Rydberg-atom probe and measurement instrument

AbstractWe present electric field measurements and imaging of a Yagi–Uda antenna near-field using a Rydberg atom–based radio frequency electric field measurement instrument. The instrument uses electromagnetically induced transparency with Rydberg states of cesium atoms in a room-temperature vapor and off-resonant RF-field–induced Rydberg-level shifts for optical SI-traceable measurements of RF electric fields over a wide amplitude and frequency range. The electric field along the antenna boresight is measured using the atomic probe at a spatial resolution ofλRF/2${\lambda }_{RF}/2$with electric field measurement uncertainties below 5.5%, an improvement to RF measurement uncertainties provided by existing antenna standards.