Total Polarization Research Articles

Deep Ultraviolet BGaN Quantum Dot structures

This research studies boron-containing quantum dot (QD) structures that emit the ultraviolet. Ternary and quaternary lattice-matched structure:, , , , ,, , and and their TE and TM gain spectra, spontaneous emission, spontaneous polarization, and piezoelectric polarization have been examined in these structures. They have high TE and TM spectra under reducing boron content in the QD or barrier layer. The total polarization decreases for the Al-containing systems, which is preferred. Binary systems emit at 199nm, while the quaternary can have a peak wavelength near 235nm. Elongating of the wavelength to 290nm is possible with with high gain at a few boron contents.

Controlling Antiferromagnetic Magnon Polarization by Interfacial Exchange Interaction

We demonstrate highly efficient control of antiferromagnetic (AFM) magnon spins by the interfacial exchange interaction in heterostructures of ferrimagnetic yttrium iron garnet (YIG) and AFM ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$. At low temperatures, ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ is antiferromagnetically ordered. The interfacial exchange interaction exerted by YIG lifts the degeneracy between the AFM magnon modes in ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$, resulting in a net spin polarization and a spin current dominated by left-handed magnons, even at zero magnetic field, which is detected by the spin Seebeck effect with a 5-nm-thick $\mathrm{Pt}$ film. In the AFM magnon-dominated region, even if the magnetic field is not sufficiently strong to induce the spin-flop transition in ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$, the total spin Seebeck signal polarity flips when the YIG magnetization switches. It clearly indicates that the ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ magnon polarization is controlled by YIG magnetization through the interfacial exchange interaction. The demonstration of the efficient control of AFM magnon polarization opens a pathway to manipulate AFM magnon quantum states using FM-AFM heterostructures.

Numerical investigation on the polarization and thermal characteristics of LiFePO4-based batteries during charging process

• An electrochemical-thermal couple model is developed for pouch lithium-ion batteries. • Effects of charge rate on polarization and heat generation are numerically studied. • Sudden rises in total polarization are mainly linked to solid-phase diffusion polarization. • Over 85% of the heat in the cell core under 8C charging comes from irreversible heat. • Charge energy efficiency of the cell at different current levels is further analyzed. High-current charging exacerbates internal polarization and abnormal heat generation, stymieing the development of fast-charging technology for lithium-ion batteries. Based on battery disassembly and charge test experiments, an electrochemical-thermal coupling model was developed and validated in this paper. The variation patterns of various polarization and heat generation of pouch-type lithium iron phosphate (LFP) batteries at different charge rates and their influence mechanisms were investigated numerically. Results indicate that the changes in charge voltage profiles are strongly linked to total cell polarization, and excessive charge current aggravates internal polarization, with the average polarization voltage reaching 109.2 mV at 8C, which is 471.7% higher than at 1C. The polarization in the electrodes dominates the cell polarization, especially at the negative electrode. Activation polarization accounted for the largest share of electrode polarization, the change in polarization profiles in the initial and final stages depended mainly on the solid-phase diffusion polarization. Besides, the large cell temperature difference at high charge currents is attributed to the order of magnitude difference in heat generation rates between the positive tab and the cell core. The cell temperature rise is primarily due to heat production in the cell core, where the proportion of irreversible heat increases nonlinearly with the charge rate, exceeding 85% of the total heat generation at 8C. The charge energy efficiency reduces gradually with increasing charge rate and is only 0.948 at 8C. These findings will help to develop appropriate charging protection strategy for better battery operation and life.

Stability of infiltrated cathodes using Pr2NiO4+delta precursor for low-temperature fuel cell applications

The electrochemical performance and stability of infiltrated praseodymium nickelate (PNO) as the cathode for solid oxide fuel cell (SOFC) applications was studied. PNO cathode (Pr2NiO4+δ) was infiltrated into gadolinium-doped ceria (GDC) scaffolds and tested in two different anode-supported cells with tubular geometry: i) tubular cell A with Ni-YSZ support, Ni-YSZ anode functional layer (AFL), and thin (∼7 μm) electrolyte and; ii) microtubular cell B with Ni-YSZ support, without AFL and thick (34 μm) electrolyte. Both cells were stable during 91 h and 260 h of stability testing at 650 °C and experienced a reduction in total polarization resistances. Post-mortem X-ray diffraction (XRD) analysis confirmed PNO's partial transformation into the Pr4Ni3O10 phase with higher electrical conductivity and thermal stability. Improvement in the oxygen reduction reaction was confirmed using DRT analysis. This finding confirms that PNO infiltrated into GDC scaffold can be considered a promising cathode for SOFC applications.

Natural Language Processing Approaches for Automated Multilevel and Multiclass Classification of Breast Lesions on Free-Text Cytopathology Reports.

The extensive growth and use of electronic health records (EHRs) and extending medical literature have led to huge opportunities to automate the extraction of relevant clinical information that helps in concise and effective clinical decision support. However, processing such information has traditionally been dependent on labor-intensive processes with human errors such as fatigue, oversight, and interobserver variability. Hence, this study aims at the processing of EHRs and performing multilevel and multiclass classification by fetching dominant characteristic features that are sufficient to detect and differentiate various types of breast lesions. In this study, unstructured EHRs on breast lesions obtained through fine-needle aspiration cytology technique are considered. The raw text was normalized into structured tabular form and converted to scores by performing sentiment analysis that helps to decide the total polarity or class label of the EHR. Supervised machine learning approaches, namely random forest and feed-forward neural network trained using Levenberg-Marquardt training function, are used for classification of the collected EHR data set containing 2,879 records that are split in the ratio of 80:20 as training and testing data sets, respectively. Random forest and feed-forward neural network classifiers gave the best performance with an accuracy of 99.36%, an overall receiver operating characteristic-area under the curve of 99.2%, a correlation with ground truth of 98.3%, and a histopathologic correlation of 98.6%. Natural language processing has huge potential to automate the extraction of clinical features from breast lesions. The proposed multilevel and multiclass classification approach is used to classify 13 different types of breast lesions with 20 different labels into five classes to decide the type of treatment that should be given to patients by a physician or oncologist.

Electron and Positron Scattering from Precious Metal Atoms in the eV to MeV Energy Range

This article reports on the scattering of unpolarized and spin polarized electrons and positrons from 28Ni58,29Cu63,46Pd108, and 78Pt196, covering light to heavy precious metal targets. To cover the wide energy domain of 1 eV ≤Ei≤300 MeV, Dirac partial-wave phase-shift analysis is employed, using a complex optical potential for Ei≤1 MeV and a potential derived from the nuclear charge distribution for Ei>1 MeV. Results are presented for the differential and integral cross-sections, including elastic, momentum transfer, and viscosity cross-sections. In addition, the inelastic, ionization, and total (elastic + inelastic) cross-section results are provided, together with mean free path estimates. Moreover, the polarization correlations S,T, and U, which are sensitive to phase-dependent interference effects, are considered. Scaling laws with respect to collision energy, scattering angle, and nuclear charge number at ultrahigh energies are derived using the equivalence between elastic scattering and tip bremsstrahlung emission. In addition, a systematic analysis of the critical minima in the differential cross-section and the corresponding total polarization points in the Sherman function S is carried out. A comparison with existing experimental data and other theoretical findings is made in order to test the merit of the present approach in explaining details of the measurements.

Ocean signatures in the total flux and polarization spectra of Earth-like exoplanets

Context. Numerical simulations of starlight that is reflected by Earth-like exoplanets predict habitability signatures that can be searched for with future telescopes. Aims. We explore signatures of water oceans in the flux and polarization spectra of this reflected light. Methods. With an adding-doubling algorithm, we computed the total flux F, polarized flux Q, and degree of polarization Ps of starlight reflected by dry and ocean model planets with Earth-like atmospheres and patchy clouds. The oceans consist of Fresnel reflecting surfaces with wind-ruffled waves, foam, and wave shadows, above natural blue seawater. Our results are presented as functions of wavelength (from 300 to 2500 nm with 1 nm resolution) and as functions of the planetary phase angle from 90° to 170°. Results. The ocean glint increases F, |Q|, and Ps with increasing phase angle at nonabsorbing wavelengths, and causes the spectra of F and |Q| for the various phase angles to intersect. In the near-infrared, Q is negative, that is, the direction of polarization is perpendicular to the plane through the star, planet, and observer. In the Ps spectra, the glint leaves dips (instead of peaks) in gaseous absorption bands. All those signatures are missing in the spectra of dry planets. Conclusions. The dips in Ps and the negative Q in the near-infrared can be searched for at a phase angle of 90°, where the planet-star separation is largest. Those ocean signatures in polarized light do not suffer from false positive glint signals that could be due to clouds or reflecting dry surfaces. For heavily cloudy planets, ocean detection is possible when the glint is (partially) cloud-free. When modeling signals of planets with oceans, using horizontally inhomogeneous cloud covers is thus crucial. Observations spread over time would increase the probability of catching a cloud-free glint and detecting an ocean.

NIKA 150 GHz polarization observations of the Crab nebula and its spectral energy distribution (Corrigendum)

The Crab nebula is a supernova remnant exhibiting a highly polarized synchrotron radiation at radio and millimeter wavelengths. It is the brightest source in the microwave sky with an extension of 7 by 5 arcminutes and commonly used as a standard candle for any experiment which aims at measuring the polarization of the sky. Though its spectral energy distribution has been well characterized in total intensity, polarization data are still lacking at millimetre wavelengths. We report in this paper high resolution (18 arcsec FWHM) observations of the Crab nebula in total intensity and linear polarization at 150 GHz with the NIKA camera. NIKA, operated at the IRAM 30 m telescope from 2012 to 2015, is a camera made of Lumped Element Kinetic Inductance Detectors (LEKIDs) observing the sky at 150 and 260 GHz. From these observations we are able to reconstruct the spatial distribution of the polarization degree and angle of the Crab nebula, which is found to be compatible with previous observations at lower and higher frequencies. Averaging across the source and using other existing data sets we find that the Crab nebula polarization angle is consistent with being constant over a wide range of frequencies with a value of -87.7$^\circ$ +- 0.3 in Galactic coordinates. We also present the first estimation of the Crab nebula spectral energy distribution polarized flux in a wide frequency range: 30-353 GHz. Assuming a single power law emission model we find that the polarization spectral index $\beta_{pol}$ = - 0.347 +- 0.026 is compatible with the intensity spectral index $\beta$ = - 0.323 +- 0.001.

Domain switching dynamics in topological antiferroelectric vortex domains

Hexagonal manganites can exhibit intriguing ferroelectric (FE) and partially undistorted antiferroelectric (PUA) ${Z}_{6}$-vortex domain patterns, which are dual to each other. Due to the same origin, it can be expected that the two real-space topological structures will behave the same way in terms of nonelectric properties such as domain topology and scaling of vortex density. However, their electric properties would be very different from each other, while these differences are rarely understood due to the absence of investigation on PUA ${Z}_{6}$-vortex domain patterns. In this work, we study the response of the PUA $P\text{\ensuremath{-}}3c1$ structure to external electric fields and the switching dynamics of PUA ${Z}_{6}$-vortex domain patterns by combining Landau theory and phase-field simulations. We find that an electric field along the $c$ axis can tune the trimerizing tilting angle of the ${\mathrm{MnO}}_{5}$ trigonal bipyramids in PUA $P\text{\ensuremath{-}}3c1$ structure while no such effect is present in the FE $P{6}_{3}cm$ structure. As a result, a continuous phase transition sequence $P\text{\ensuremath{-}}3c1\ensuremath{\rightarrow}P3c1\ensuremath{\rightarrow}P{6}_{3}cm$ can be induced. For both the PUA ${Z}_{6}$-vortex domain pattern and the single PUA domain, the variation of the total polarization with a sinusoidal electric field manifests as a double-hysteresis loop. We find out that this is because the transition from $P{6}_{3}cm$ back to $P3c1$ is a first-order transition. The switching dynamics of PUA ${Z}_{6}$-vortex domain patterns is found to be very different from that observed on FE ${Z}_{6}$-vortex domain patterns. Our results advance the understanding of real-space topological structures and suggest that the PUA $P\text{\ensuremath{-}}3c1$ structure may exhibit excellent performance in dielectric energy storage.

Strong Linearly Polarized Emission from Monolayer WS2 Coupled with Plasmonic Nanocavity Array

AbstractAs an indispensable component of optoelectronic system, an on‐chip light source with well‐defined polarization is desirable in optical communication, signal processing and display applications. The emerging atomically thin transition metal dichalcogenides (TMDCs), due to their high quantum yield and robust valley coherence, provide an unprecedented platform to realize the high‐efficient linearly polarized light emission. Although the valley‐related optical selection rules suggest that valley coherence should be possible, extreme conditions such as cryogenic temperatures are required, which is a long‐term challenge for their practical applications. In this paper, the strongly enhanced linearly polarized emission is realized by integrating WS2 monolayers with a delicate designed plasmonic nanocavity. It is demonstrated that strong plasmon–exciton coupling gives rise to the plasmon–exciton polariton. The polariton valley coherence results in a linear polarization up to 0.32 at room temperature and contributes to 52% of the total linear polarization. Enhancement of linear polarization through polariton valley coherence can be understood as the consequence of the extra relaxation channel introduced by its plasmonic counterpart. The potential of 2D TMDC‐plasmon hybrid structure appears to be high and of significant technological interest, as well as inspires new perspectives on quantum manipulations in 2D solid‐state systems.

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

Surface interactions are responsible for many properties of condensed matter, ranging from crystal faceting to the kinetics of phase transitions. Usually, these interactions are polar along the normal to the interface and apolar within the interface. Here we demonstrate that polar in-plane surface interactions of a ferroelectric nematic NF produce polar monodomains in micron-thin planar cells and stripes of an alternating electric polarization, separated by {180}^{{{{{{rm{o}}}}}}} domain walls, in thicker slabs. The surface polarity binds together pairs of these walls, yielding a total polarization rotation by {360}^{{{{{{rm{o}}}}}}}. The polar contribution to the total surface anchoring strength is on the order of 10%. The domain walls involve splay, bend, and twist of the polarization. The structure suggests that the splay elastic constant is larger than the bend modulus. The {360}^{{{{{{rm{o}}}}}}} pairs resemble domain walls in cosmology models with biased vacuums and ferromagnets in an external magnetic field.

Local and global polarization of Λ hyperons across RHIC-BES energies: The roles of spin hall effect, initial condition, and baryon diffusion

We perform a systematic study on the local and global spin polarization of $\mathrm{\ensuremath{\Lambda}}$ and $\overline{\mathrm{\ensuremath{\Lambda}}}$ hyperons in relativistic heavy-ion collisions at beam energy scan energies via the ($3+1$)-dimensional CLVisc hydrodynamics model with a multiphase transport (AMPT) and simulating many accelerated strongly interacting hadron (SMASH) initial conditions. Following the quantum kinetic theory, we decompose the polarization vector as the parts induced by thermal vorticity, shear tensor and the spin Hall effect (SHE). We find that the polarization induced by the SHE and the total polarization strongly depends on the initial conditions. At $7.7\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$, the SHE gives a sizable contribution and even flips the sign of the local polarization along the beam direction for the AMPT initial condition, which is not observed for the SMASH initial condition. Meanwhile, the local polarization along the out-of-plane direction induced by the SHE with the AMPT initial condition does not always increase with decreasing collision energies. Next, we find that the polarization along the beam direction is sensitive to the baryon diffusion coefficient, but the local polarization along the out-of-plane direction is not. Our results for the global polarization of $\mathrm{\ensuremath{\Lambda}}$ and $\overline{\mathrm{\ensuremath{\Lambda}}}$ agree well with the data of the STAR Collaboration. Interestingly, the global polarization of $\overline{\mathrm{\ensuremath{\Lambda}}}$ is not always larger than that of $\mathrm{\ensuremath{\Lambda}}$ due to various competing effects. Our findings are helpful for understanding the polarization phenomenon and the detailed structure of quark-gluon plasma in relativistic heavy-ion collisions.

Enhancement corrosion resistance of mild steel in 15% HCl solution by a novel bio-based polyurethane for oil well acidizing

A novel thermally stable inhibitor was developed based on citric acid and glucose (CAGCI) to inhibit the corrosion of mild steel (MS) in simulated acidic oilfield water for oil well acidizing. All electrochemical measurements were performed in a temperature range of 293–363 K to evaluate the inhibition power of CAGCI. The results of electrochemical tests clearly revealed that CAGCI effectively inhibited MS corrosion via a mixed-type mechanism and 77 × 10−4 M of the inhibitor provided the highest inhibition efficiency of 90%, 93.6%, 93.7%, and 89.9% at 293 K, 313 K, 333 K, and 363 K, respectively. In addition, CAGCI provided a total polarization resistance of 416.7 Ω cm2 for MS at 293 K and decreased the corrosion rate of the metal 7.6 times compared to blank at 363 K. Moreover, the UV–visible results demonstrated the formation of the Fe2+-CAGCI complex and the results of the surface analysis confirmed the presence of a protective film of CAGCI molecules on the MS surface. Finally, the experimental outcomes were well complemented by results obtained from density-functional study and molecular dynamics (MD) simulation. According to quantum calculations, citric acid and aromatic rings in the structure of CAGCI played the main role in electron exchanges with the MS surface. The results of the MD simulation were also confirmed that a hydrophobic barrier can be formed by CAGCI molecules on the MS surface with a parallel adsorption configuration.

Mueller matrix spectroscopic ellipsometry

Abstract The Mueller matrix is a mathematical description of how light is altered by an optical element or a sample under study. It describes both intensity (irradiance) and polarization changes, including a reduction of the total polarization. Mueller matrix spectroscopic ellipsometry has gained recent popularity in the optics and semiconductor communities as an effective means to characterize complex sample structures and anisotropic materials. While this method is not new, its recent expansion to new fields has left many users with only a pedestrian understanding of the data they collect. This tutorial provides an overview of Mueller matrix spectroscopic ellipsometry with focus on practical aspects for those new to the technique.

Observability of negative capacitance of a ferroelectric film: Theoretical predictions

We theoretically explore mechanisms that can potentially give rise to the steady-state and transient negative capacitance in a uniaxial ferroelectric film stabilized by a dielectric layer. The analytical expressions for the steady-state capacitance of a single-domain and polydomain states are derived within the Landau-Ginzburg-Devonshire approach and used to study the state stability vs the domain splitting as a function of dielectric layer thickness. Analytical expressions for the critical thickness of the dielectric layer, polarization amplitude, equilibrium domain period, and susceptibility are obtained and corroborated by finite element modeling. We further explore the possible effects of nonlinear screening by two types of screening charges at the ferroelectric-dielectric interface and show that if at least one of the screening charges is very slow, the total polarization dynamics can exhibit complex time- and voltage-dependent behaviors that can be interpreted as an observable negative capacitance. In this setting, the transient negative capacitance effect is accompanied by almost zero dielectric susceptibility in a wide voltage range and low frequencies. These results may help to elucidate the observation of the transient negative capacitance in thin ferroelectric films, and identify materials systems that can give rise to the behavior.

Computation of flexoelectric coefficients of a MoS2 monolayer with a model of self-consistently distributed effective charges and dipoles.

Flexoelectricity is an electromechanical coupling phenomenon that can generate noticeable electric polarization in dielectric materials for nanoscale strain gradients. It is gaining increasing attention because of its potential applications and the fact that experimental results were initially an order of magnitude higher than initial theoretical predictions. This stimulated intense experimental and theoretical research to investigate flexoelectric coefficients in dielectric materials such as two-dimensional materials. In this study, we concentrate on the calculation of the flexoelectric coefficients of 2D-MoS2 due to a model using self-consistently determined charges and dipoles on the atoms. More specifically, we study the importance of two contributions that were neglected/omitted in previous papers using this model, namely, the charge term in the total polarization and the conservation of electric charge through a Lagrange multiplier. Our calculations demonstrate that the results for flexoelectric coefficients computed with this improved definition of polarization agree better with experimental measurements, provided that consistent definitions for signs are used. Additionally, we show how two physical contributions with opposite signs compete to give net values of flexoelectric coefficients that can be either positive or negative depending on their relative importance and give net values for the case of MoS2.

Generation of polarized proton beams with gaseous targets from CO2-laser-driven collisionless shock acceleration

We propose obtaining polarized proton beams based on CO2-laser-driven collisionless shock acceleration (CSA) of the pre-polarized HCl gas. By tailoring the density profile of the pre-polarized HCl gas, the intense CO2 laser pulse heats the plasma target and forms a strong shock that reflects the polarized protons to high energy. According to particle-in-cell simulations implemented with the spin dynamics, directional proton beams of several MeV were generated at a total beam polarization of over 80%. Simulations showed that proton spin precession occurred in the azimuthal magnetic fields generated by the Biermann effect and plasma currents. The latter was the main depolarization mechanism in the early stage of shock wave formation. For CSA at CO2 laser intensities around 1017–1018 W/cm2, the proton depolarization was insignificant and the beam polarization purity was preserved. As pre-polarized hydrogen targets were available at gaseous densities in-state-of-art facilities, CSA driven by relatively long wavelength lasers provided a feasible solution for obtaining ultra-fast polarized proton sources.

Dielectric Properties of Carbon-Like Nanotube Structure: Monte Carlo Study

In this paper, we study the thermal and dielectric properties of a carbon-like nanotube structure. The ferrielectric mixed spin (1,3/2) Blume–Capel Ising model has been investigated, using Monte Carlo simulations under the Metropolis algorithm. We illustrate the thermal and dielectric properties of different physical parameters. Besides, we examine the effects of the exchange coupling interactions, the external longitudinal electric and the crystal fields on the transition temperature. It is found that the polarization decreases toward a transition temperature and undergoing the paraelectric phase, faster for low values of the external longitudinal electric field and the exchange coupling interactions. Besides, the total polarization versus the crystal field undergoes two principal transitions and exhibits a first-order and a second-order transitions.

Hydrodynamic helicity polarization in relativistic heavy ion collisions

We study helicity polarization through the $(3+1)$-dimensional relativistic viscous hydrodynamic models at $\sqrt{{s}_{NN}}=200$ GeV $\text{Au}+\text{Au}$ collisions. Similar to the local spin polarization, we consider the helicity polarization beyond global equilibrium and investigate the contributions induced by thermal vorticity, shear viscous tensor, and the fluid acceleration. We find that the local helicity polarization induced by thermal vorticity dominates over other contributions. It also implies that, in low-energy collisions, the fluid vorticity as part of thermal vorticity may play the crucial role in the total helicity polarization. Such a finding could be useful for probing the local strength of vorticity in rotational quark gluon plasmas by measuring helicity polarization. Our simulation confirms the strict space reversal symmetry, whereas we also compare our numerical results with approximated relations derived from ideal Bjorken flow. Our studies also provide a baseline for the future investigation on local parity violation through the correlations of helicity polarization.

Hyperon production in quasielastic ν¯τ−nucleon scattering

The theoretical results for the total cross sections and polarization components of the $\tau^{+}$ lepton produced in the charged current induced $|\Delta S| = 1$ quasielastic $\bar\nu_\tau - N$ scattering leading to hyperons ($\Lambda, \Sigma$) have been presented assuming T invariance. The theoretical uncertainties arising due to the use of different vector, axial vector and pseudoscalar form factors as well as the effect of SU(3) symmetry breaking have been studied. We have also presented, for the first time, a comparison of the total cross sections for the production of $e,\mu,\tau$ leptons to facilitate the implications of lepton flavor universality~(LFU) in the $|\Delta S| = 1$ quasielastic reactions induced by the antineutrinos of all flavors i.e., $\nu_{l};~l=e,\mu,\tau$.