Theory Of Polarization Research Articles

Electron accumulation and distribution at interfaces of hexagonal ScxAl1−xN/GaN- and ScxAl1−xN/InN-heterostructures

Electron charges and distribution profiles induced by polarization gradients at the interfaces of pseudomorphic, hexagonal ScxAl1−xN/GaN- and ScxAl1−xN/InN-heterostructures are simulated by using a Schrödinger–Poisson solver across the entire range of random and metal-face ScxAl1−xN-alloys, considering the transition from wurtzite to hexagonal layered crystal structure. In contrast to previous calculations of polarization-induced sheet charges, we use Dryer’s modern theory of polarization, which allows for consideration of the spontaneous polarization measured on ferroelectric ScxAl1−xN-layers. Because the sheet density of the electrons accumulating at the heterostructure interfaces can strongly depend both on the data set of the piezoelectric and structural coefficients and on the alloying region of the ScxAl1−xN-layers in which the transition from the wurtzite to the hexagonal layered crystal structure occurs, we have calculated the charge carrier sheet densities and profiles for three representative data sets and evaluated their relevance for devices. We predict electron sheet densities of (2.26±0.20)×1014cm−2 and (6.25±0.20)×1014cm−2 for all three sets of data for Ni/AlN/InN- and Ni/ScN/InN-heterostructures, respectively. We demonstrate that the polarization-induced interface charges of Ni/ScxAl1−xN/InN-heterostructures are always positive, tend to increase with increasing Sc-content, and can cause electron accumulations that lead to flooding of the triangular quantum wells at the semiconductor interface. We identify Ni/ScxAl1−xN/GaN-heterostructures with 0.13≤x≤0.19 as particularly promising candidates for the processing of energy-efficient high electron mobility transistors due to their missing or low mechanical strain and their large electron sheet densities between (4.11±0.20)×1013cm−2 and (6.37±0.20)×1013cm−2. Furthermore, we present simulation results of highly strained Ni/ScxAl1−xN/GaN-heterostructures for 0.81≤x≤1.0, which point to electron accumulations of up to (8.02±0.40)×1014cm−2. These heterostructures are not suitable for transistor devices, but they may be of great interest for the implementation of low impedance contacts.

Primary Divisions: How Voters Evaluate Policy and Group Differences in Intraparty Contests

While central to theories of polarization and primary elections, surprisingly little evidence shows that partisans favor candidates who take ideologically consistent issue positions, above other considerations, in intraparty contests. In this study, we investigate how voters weigh policy and nonpolicy differences when evaluating same-party politicians, using novel conjoint experiments that manipulate the demographic, biographical, and issue information of congressional candidates. We recruit 4,093 participants in the 2016 Cooperative Congressional Election Study, assigning half to either rate same-party candidates on an ideological scale or choose between them in primary-like settings. We find that voters place candidates along coherent policy lines and give greater support to those taking party-consistent issue positions. We also find evidence of affinity voting on shared racial, gender, and religious characteristics, though effects are typically smaller. Our results underscore how informed partisans’ policy attitudes can drive choices in primary elections, including which candidates contest them.

Calculation of the spin-lattice relaxation time and the activation energy near the IV–III phase transition in pyridinium fluorosulfonate (C5NH6)FSO3

The spin-lattice relaxation time T1 H for protons nuclei is calculated in term of the pseudospin–phonon (PS) coupled and the energy fluctuation (EF) models close to the IV–III solid–solid phase transition of in (C5NH6)FSO3. This calculation was performed by associating the observed second moment of the 1H as the order parameter below T C and the disorder parameter above T C. Values of the activation energy for the cation reorientation in this crystal are also deduced by using both models. In addition, the observed dielectric permittivity of this crystal is analyzed within the framework of the Landau theory and values of the spontaneous polarization (P S) are determined as a function of temperature. The normalized values of P S are used in the PS and EF models to extract the activation energy for the reorientation of the dipole moment of this compound arising from cation–anion interaction. Our results show that the PS and EF models can describe the observed behavior of the spin-lattice relaxation time adequately for the IV–III solid–solid transition in (C5NH6)FSO3.

Role of CuO in Al2O3-B2O3 Composites: In Situ Phases, Density, Hardness, and Wear Resistance

Abstract The aim of this study was to develop a novel set of Al2O3-B2O3-CuO composites and evaluate their tribological performance at varying humidity (10–95% relative humidity) levels. First, the Al2O3-B2O3 composites were prepared using cold press sintering by varying the amount of B2O3 (5–20 wt%). The results revealed that an increase in B2O3 content in the composites increased the amount of aluminum borate in situ phase during sintering. The presence of the aluminum borate phase in the composite enhanced the hardness and wear resistance, whereas the humidity-sensitive alumina phase reduced friction at higher humidity levels. Next, CuO (5 wt%) was added to the Al2O3-B2O3 composites to form Al2O3-B2O3-CuO composites. These composites showed an increase in the percentage relative density by 16–37% and hardness by 1.2–1.9 times. Subsequently, the tribological performance was improved significantly. The underlying mechanism for improved wear resistance was discussed using the crystal-chemical approach and polarization theory to guide the design of these novel Al2O3-B2O3-CuO composites.

Ideological and partisan biases in ratings of candidate quality in U.S. House elections

AbstractObjectiveThis article explores whether voters evaluate candidates’ ideology, partisanship, and quality independently or exhibit behavior consistent with motivating reasoning, rating co‐partisans and candidates ideologically similar to themselves as more competent.MethodsUsing a survey of voters and experts from 2010 U.S. House elections, I estimate a model predicting an individual's rating of incumbent candidate competence for office and challenger candidate competence for office.ResultsIndividuals ideologically distant from a candidate rate the candidate as less competent, yet rate co‐partisan candidates as more competent. For incumbents, opposing partisanship amplifies the negative effect of ideological distance on candidate quality ratings, and shared partisanship mitigates the negative effect of ideological distance.ConclusionOnly incumbents rated as the most competent can overcome the ideological and partisan biases of voters. Consistent with theories of affective polarization, these results imply that polarization runs deeper than partisan or ideological differences–it is personal.

Many-body quadrupolar sum rule for higher-order topological insulators

The modern theory of polarization establishes the bulk-boundary correspondence for the bulk polarization. In this paper, we attempt to extend it to a sum rule of the bulk quadrupole moment by employing a many-body operator introduced in Kang et al. [B. Kang, K. Shiozaki, and G. Y. Cho, Phys. Rev. B 100, 245134 (2019)] and Wheeler et al. [W. A. Wheeler, L. K. Wagner, and T. L. Hughes, Phys. Rev. B 100, 245135 (2019)]. The sum rule that we propose consists of the alternating sum of four observables, which are the phase factors of the many-body operator in different boundary conditions. We demonstrate its validity through extensive numerical computations for various noninteracting tight-binding models. We also observe that individual terms in the sum rule correspond to the bulk quadrupole moment, the edge-localized polarizations, and the corner charge in the thermodynamic limit on some models.

Role of B2O3 and CaO in Al2O3 matrix composite: In-situ phases, density, hardness and wear resistance

A novel set of Al2O3-B2O3-CaO composites were manufactured using a cold press-sintering. The B2O3 content in the composites was varied from 5 to 20 wt% and 2 wt% CaO was added to the composites. Dry sliding tests were conducted against an alumina ball at 10–95% relative humidity. The presence of the in-situ formed aluminum borate in the composite enhanced the micro-hardness and wear resistance, whereas the humidity-sensitive alumina phase reduced friction. Furthermore, addition of CaO improved the relative density upto ~92% which also led to significant improvement in hardness and wear resistance. However, the friction was negatively affected. The mechanism for enhanced wear resistance is demonstrated by considering the crystal-chemical approach and polarization theory for the double oxide systems.

Field theory of structured liquid dielectrics

We develop a field-theoretic approach for the treatment of both the nonlocal and the nonlinear response of structured liquid dielectrics. Our systems of interest are composed of dipolar solvent molecules and simple salt cations and anions. We describe them by two independent order parameters, the polarization field for the solvent and the charge-density field for the ions, including and treating the nonelectrostatic part of the interactions explicitly and consistently. We show how to derive functionals for the polarization and the electrostatic field of increasingly finer scales and solve the resulting mean-field saddle-point equations in the linear regime. We derive criteria for the character of their solutions that depend on the structural lengths and the polarity of the solvent. Our approach provides a systematic way to derive generalized polarization theories.

Temperature dependence of the strain of the AlGaN barrier layer under the gate in AlGaN/AlN/GaN HFETs

By a combination of electrical measurement, the Debye model and the basic theory of polarization, the strain of AlGaN barrier layer underneath the gate in two AlGaN/AlN/GaN HFETs at the same ratio of gate length (LG) to source-drain distance (LSD) but with different dimensions is investigated at temperatures from 300 ​K to 450 ​K. It is found that temperatures have important influence on this strain. Furthermore, the temperature dependence of the strain is found related to device dimensions, a phenomenon that can be explained by the Ohmic contact metal atoms diffusion nearby the Ohmic electrode and lattice mismatch underneath the gate electrode. This study is conducive to understanding the effect of temperatures on the polarization Coulomb field (PCF) scattering, which has been verified to be a significant scattering mechanism affecting the performance of AlGaN/AlN/GaN HFETs.

Automated media and commercial populism

ABSTRACT This article considers the link between the increasingly important role of automated information curation online and the rise of what we call ‘commercial populism’. We invoke the term to refer to the convergence of populism as a marketing tool – a way of selling, for example, nutritional supplements or survivalist merchandise – with political strategies that cater to the citizen as consumer (whose freedoms are framed in the individual register of personal taste unfettered from civic concerns or constraints). Perhaps unsurprisingly in this context, we draw on the example of Donald Trump's political rise, which while not unrelated to his particular idiosyncrasies, demonstrates how the automated curation of social media aligns itself with what the aggressive rise of commercial populism. The goal of such an analysis is to consider how the combination of hyper-commercialism with the formal attributes of social media contributes to inter-related political pathologies of polarization and conspiracy theory. The consumer-oriented model of personal taste catered to by algorithmic curation highlights the paradox of ‘social’ media: they promise to enhance the social by displacing or reframing it fundamental a-social. The offloading of social decisions and formation onto commercial, automated systems for curating news and information reinforces this version of individualism, contributing to the forms of misrecognition that enable it.

Thermoelectric Polarization Transport in Ferroelectric Ballistic Point Contacts.

We formulate a scattering theory of polarization and heat transport through a ballistic ferroelectric point contact. We predict a polarization current under either an electric field or a temperature difference that depends strongly on the direction of the ferroelectric order and can be detected by its magnetic stray field and associated thermovoltage and Peltier effect.

Research on opinion polarization by big data analytics capabilities in online social networks

Opinion polarization in online social networks causes a lot of concerns on its social, economic, and political impacts, and is becoming an important topic for academic research. Based on the system theory, a theoretical framework on analyzing opinion polarization combining big data analytics capabilities (BDAC) is proposed. A web crawler is used to collect data from the Sina Weibo platform on the topic of “Tangping”. Concerning the characteristics of the big data environment, social network analysis (SNA), machine learning, text clustering and content analysis are used to mine opinion polarization of “Tangping” on Weibo. Results show that social network users holding the same opinion indicate the phenomenon of aggregation. Although no influential users support the opinion of “Tangping” on Weibo, a high percentage of people advocate the idea. The supporting group has the most clusters while the opposing group has the highest density of keywords. The research contributes to the existing literature on applying BDAC to analyze online polarization from the perspective of the system from user behavior and interaction to topic clustering and keywords identification. The conceptual system framework shows superiority in the integration of information coordination of microsystem and exosystem. Guidance strategies are put forward to supplement the formation theory of opinion polarization and provide suggestions to reasonably regulate network group polarization.

Real-time monitoring of organic contaminant adsorption in activated carbon filters using spectral induced polarization

Real-time, in-situ monitoring of adsorption processes in activated carbon (AC) filters may advance the effectiveness, reliability and economical value of such systems. In this study, the applicability of spectral induced polarization (SIP) as a real-time monitoring tool was examined. The adsorption of anionic and cationic organic dyes to commercial-AC filter was examined using a set of breakthrough experiments combined with continuous SIP monitoring. The imaginary part of the complex electrical conductivity decreased in the range of 0.25−2.5Hz for both dyes. During the adsorption of the cationic dye, a new peak developed in the range of 7−40Hz, suggesting the dominance of surface processes that are not explained by the classic stern-layer polarization theory. The recorded imaginary conductivity values were used as a proxy for adsorbed dye concentration in the calibration process of a reactive transport model. The model confirmed that SIP can successfully be used for real-time monitoring of the dye progression through the filter. The applicability of SIP as an effective monitoring tool was also shown for cyclic operation (adsorption-desorption cycles).

Average intensity and polarization evolution of aberrated partially coherent cosh-Airy beams propagating in ocean turbulence

In this paper, the cross-spectral density (CSD) of aberrated cosh-Airy beams in oceanic turbulence is first derived. And then, the corresponding CSD matrix elements can be obtained by the unified theory of coherence and polarization. Finally, the features of astigmatic cosh-Airy beams propagating in ocean turbulence, i.e. average intensity, spectral coherence and polarization properties, were investigated in detail using numerical simulation. It can be found that the astigmatism has different effects on the average intensity in x and y directions. And the distance of the polarization returning to its initial value is affected by the astigmatism coefficient, cosh modulation parameters and coherence length.

Analysis and experimental demonstration of propagation features of radially polarized specific non-uniformly correlated beams.

With the development of the unified theory of coherence and polarization, the novel physical properties generated by different correlation structures of vector partially coherent beams (PCBs) have attracted much attention. Recently, a new class of structured beams have been proposed [Opt. Lett.45, 3824 (2020)10.1364/OL.397316], called vector specific non-uniformly correlated beams. These beams combine non-uniform polarization and non-uniform correlation, and they exhibit propagation features not seen in conventional vector PCBs. In this Letter, we continue the analysis of the previous work, taking radially polarized Hermite non-uniformly correlated (RPHNUC) beams as an example, and focus on the physical interpretation of the peculiar propagation features of such beams. We verify the predicted behavior of RPHNUC beams through experiment.

Sulfonated poly(vinyl alcohol) as an artificial solid electrolyte interfacial layer for Li metal anode

The cycle performance of Li metal batteries with high energy-density is hindered by the stability of Li metal anode. In this manuscript, sulfonated poly(vinyl alcohol) (SPVA) was synthesized and used as an artificial solid electrolyte interfacial (SEI) layer to construct stable Li metal anode interface. The ionic conductivity of SPVA coating layer in liquid electrolyte was calculated according to the theories of interfacial polarization in heterogeneous systems by dielectric method. In the Li|PE|SPVA/Cu or Li/SPVA|PE|SPVA/Li cells, Li deposits beneath the SPVA layer, surviving from the corrosion of liquid electrolyte and excessive volume expansion. Benefited from the constructed stable artificial SEI layer, the interfacial polarization and internal resistance in the symmetric cells are reduced. The cycle performance of LiFePO4|PE|SPVA/Li cell has been greatly improved, which could be stably cycled for more than 500 cycles.

Change Detection in Dual Polarization Sentinel-1 Data With Wilks’ Lambda

When the covariance matrix formulation is used for multilook polarimetric synthetic aperture radar (SAR) data, Wilks' Lambda can be used for change detection between acquisitions at two time points. We briefly describe the theory for dual polarization, diagonal only data. A case study illustrates the technique on Sentinel-1 C-band data covering the international Frankfurt Airport. We successfully detect change including direction of change in the sense that Wilks' Lambda shows whether radar signal increases or decreases over time.

Affect toward Minority and Majority Groups in the Era of Donald Trump

U.S. voters’ affect toward such minority groups as blacks, Muslims, and transgender people has become warmer in recent years. Warming affect toward minority groups is a surprise for the influential theory of affective polarization. In arguing that voters’ partisan allegiances fuel dislike of groups associated with the opposing political party, this theory predicts that it is primarily Democratic identifiers whose affect has become warmer, as affect is assumed to reflect partisanship and little more. Yet this is not what the authors find, analyzing high-quality data from the 2012–2020 American National Election Studies. Not only have Republicans (like Democrats) become warmer toward minority groups, but this influenced voter choice and contributed heavily to the outcome of the 2020 presidential election. Voters’ affect toward social groups may matter independently of the powerful force of partisanship. The authors discuss study limitations, alongside implications for affective polarization theory, research on Trumpism, and classical sociological scholarship on liberalization.

COVID-19 through a cultural lens

COVID-19 through a cultural lens

Tuning the dielectric response in a nanocomposite material through nanoparticle morphology.

Ceramic materials such as metal oxides, mixed metal oxides and silicates, constitute a broadly-used, high-performance technology for electronic insulators. The introduction of metal cluster dopants and molecular-scale inclusions in a dielectric matrix provides an opportunity for manufacturing new high-κ solid-state dielectrics with tunable field–response properties. The quantum properties of these metallic nanoparticles depend strongly on their size and shape, a characteristic that can be exploited in changing the response properties of a material, whereas the small nanoparticle size can help limit the issues of conduction and current leakage. Here, we model the polarization of molecular-scale silver inclusions in a magnesium oxide matrix, using the Modern Theory of Polarization and Car–Parrinello Molecular Dynamics (CPMD). Details of the implementation are laid out, including handling of current jumps due to the distortion of the matrix during the simulation. Several trends in the dielectric response are considered in this work, including the effects of nanoparticle size, shape and orientation relative to the applied field. Dielectric permittivity enhancements of 30–100% are observed with inclusion sizes varying from 8 to 32 atoms, considering both rod-like and disk-like inclusions, with alignment either parallel or perpendicular to the external field.