Strong Polarization Research Articles

Multitechnique study of the B[e] supergiant RMC 82

ABSTRACT B[e] supergiants (sgB[e]) are rare objects whose evolutionary stage remains uncertain. Observationally, they display strong Balmer emission lines, infrared excess, and intrinsic polarization, indicating a non-spherical circumstellar envelope. We present a study of the sgB[e] RMC 82, using new spectropolarimetric data complemented by photometry from the ultraviolet (UV) to the mid-infrared. Our two-component model comprises a slow, dense equatorial wind wherein dust grains form and a fast polar wind. We applied the hdust radiative transfer code and Bayesian statistics to infer the parameters from a grid of 3240 pre-computed models. The model accurately reproduces the spectral energy distribution and polarized spectrum, but struggles to match the H α emission. Our results suggest a large mass-loss rate of $6.6 \times 10^{-6}\, \mathrm{{\rm M}_{\odot }\, yr^{-1}\, sr^{-1}}$. The dense wind is confined within an opening angle of 11°. The hottest dust grains are located at 277 R* with a temperature of 870 K. The dust grains are porous, with a density of 0.051 $\rm {g\, cm^{-3}}$. The central star was found to be significantly hotter than previous estimates (Teff = $27\, 000$ K). By comparing models with different components, we find that gas reprocesses a significant amount of UV radiation, shielding the dust. However, the dust also scatters UV photons back to the inner disc, increasing its temperature and H α emission. We conclude that self-consistent models, that account for the gas–dust interplay in the envelope, are essential for studying sgB[e] and similar objects.

What Are the Causes of Super Activity of Solar Active Regions?

Flare productivity varies among solar active regions (ARs). This study analyzed 20 ARs of contrasting sunspot areas and flare productivities to understand the super flare productivity of certain ARs. We used the flare index (FI) as an indicator of flare activity. We examined the pattern of morphological evolution of magnetic features. Further, we derived a set of magnetic feature parameters to quantitatively characterize ARs. Our study found that the correlation coefficient is the highest (r = 0.78) between FI and the length of the strong gradient polarity inversion line (SgPIL), while the coefficient is the lowest (r = 0.14) between FI and the total unsigned magnetic flux. For the selected ARs, this study also found that the super flare productive ARs have SgPILs (R value) longer (greater) than 50 Mm (4.5). These results suggest that flare productivity is mainly controlled by the size of the subregion that comprises close interaction of opposite magnetic polarities and is weakly correlated with the size of the whole ARs. Further, even though magnetic flux emergence is important, this study shows that it alone is insufficient to increase flare productivity. New emergence can drive either the interaction of like or opposite magnetic polarities of nonconjugate pairs (i.e., polarities not from the same bipole). In the former case, the magnetic configuration remains simple, and flare productivity would be low. In the latter case, the convergence of opposite magnetic fluxes of nonconjugate pairs results in a magnetic configuration with long SgPIL and an increase in flare productivity.

Hierarchical Fe-Co@TiO2 with Incoherent Heterointerfaces and Gradient Magnetic Domains for Electromagnetic Wave Absorption.

Induced polarization response and integrated magnetic resonance show prosperous advantages in boosting electromagnetic wave absorption but still face huge challenges in revealing the intrinsic mechanism. In this work, we propose a self-confined strategy to construct hierarchical Fe-Co@TiO2 microrods with numerous incoherent heterointerfaces and gradient magnetic domains. The results demonstrate that the use of polyvinylpyrrolidone (PVP) coating is crucial for the subsequent deposition of Co-zeolitic imidazolate frameworks (ZIF-67), the distance of ordered arranged metal ions manipulates the size of magnetic domains, and the pyrolysis of PVP layers restricts the eutectic process of Fe-Co alloys to some extent. As a result, these introduced lattice defects, oxygen vacancies, and incoherent heterointerfaces inevitably generate a strong polarization response, and the regulated gradient magnetic domains realize integrated magnetic resonance, including macroscopic magnetic coupling, long-range magnetic diffraction, and nanoscale magnetic bridge connection, and both of the intrinsic mechanisms in dissipating electromagnetic energy are quantitatively clarified by Lorentz off-axis electron holography. Owing to the cooperative merits, the Fe-Co@TiO2 absorbents exhibit enhanced absorption intensity and strong absorption bandwidth. This study inspires us to develop a generalized strategy for manipulating the size of magnetic domains, and the integrated magnetic resonance theory provides a versatile methodology in clarifying magnetic loss mechanism.

Multi-Wavelength Selective and Broadband Near-Infrared Plasmonic Switches in Anisotropic Plasmonic Metasurfaces.

Anisotropic plasmonic metasurfaces have attracted broad research interest since they possess novel optical properties superior to natural materials and their tremendous design flexibility. However, the realization of multi-wavelength selective plasmonic metasurfaces that have emerged as promising candidates to uncover multichannel optical devices remains a challenge associated with weak modulation depths and narrow operation bandwidth. Herein, we propose and numerically demonstrate near-infrared multi-wavelength selective passive plasmonic switching (PPS) that encompasses high ON/OFF ratios and strong modulation depths via multiple Fano resonances (FRs) in anisotropic plasmonic metasurfaces. Specifically, the double FRs can be fulfilled and dedicated to establishing tailorable near-infrared dual-wavelength PPS. The multiple FRs mediated by in-plane mirror asymmetries cause the emergence of triple-wavelength PPS, whereas the multiple FRs governed by in-plane rotational asymmetries avail the implementation of the quasi-bound states in the continuum-endowed multi-wavelength PPS with the ability to unfold a tunable broad bandwidth. In addition, the strong polarization effects with in-plane anisotropic properties further validate the existence of the polarization-resolved multi-wavelength PPS. Our results provide an alternative approach to foster the achievement of multifunctional meta-devices in optical communication and information processing.

Tunneling Valley Hall Effect Driven by Tilted Dirac Fermions.

Valleytronics is a research field utilizing a valley degree of freedom of electrons for information processing and storage. A strong valley polarization is critical for realistic valleytronic applications. Here, we predict a tunneling valley Hall effect (TVHE) driven by tilted Dirac fermions in all-in-one tunnel junctions based on a two-dimensional (2D) valley material. Different doping of the electrode and spacer regions in these tunnel junctions results in momentum filtering of the tunneling Dirac fermions, generating a strong transverse valley Hall current dependent on the Dirac-cone tilting. Using the parameters of an existing 2D valley material, we demonstrate that such a strong TVHE can host a giant valley Hall angle even in the absence of the Berry curvature. Finally, we predict that resonant tunneling can occur in a tunnel junction with properly engineered device parameters such as the spacer width and transport direction, providing significant enhancement of the valley Hall angle. Our work opens a new approach to generate valley polarization in realistic valleytronic systems.

Fabrication of porous X-shaped Fe3O4@C core-shell structures for tunable microwave absorption

Designing porous materials with low density and high specific surface area is one of the strategies to obtain excellent wave absorbing properties. In this study, the carbon-coated porous X-shaped Fe3O4 composites used as microwave absorption materials were prepared by heat treatment of FeOOH@Polydopamine (PDA) core-shell precursors. It revealed that the X-shaped Fe3O4 core showed improved magnetic loss in GHz band due to its special shape anisotropy and large specific surface area. In addition, the modification of carbon enabled the Fe3O4 absorbers to have stronger polarization and higher electrical conductivity. The composites exhibited great freedom in performance tunability, allowing for strong absorption (RL<−40 dB) at different frequencies. For composites with thick carbon shell, the reflection loss reached the optimal value of − 64.92 dB at 15.04 GHz at the thickness of 1.75 mm, and the effective bandwidth was up to 4.64 GHz (13.04–17.68 GHz). The impressive performance of the as-prepared Fe3O4 @C core-shell composites was mainly attributed to the complementary behaviors of strong dielectric loss and magnetic loss.

Hierarchical Flower-like Sulfides with Increased Entropy for Electromagnetic Wave Absorption.

The concept of high entropy is considered promising to enhance electromagnetic wave absorption properties. However, preparing high-entropy sulfides with unique structures for high-performance electromagnetic absorption remains a challenge. In this study, hierarchical porous flower-like dual-phase sulfides were designed with increased entropy and fabricated using a versatile approach. The porous flower configuration enhanced the scattering of electromagnetic waves and the impedance-matching characteristics. Additionally, the effect of high entropy induced diverse defects that were favorable for electromagnetic wave dissipation in dual-phase sulfides. The design of the dual-phase structure generated strong interface polarization, and the composition and content of the phases exhibited clear changes with the increase in the number of metal elements. Interestingly, apparent lattice distortions, defects, and shear strains were directly observed near the dual-phase interface of millerite (102) and pyrite (220) planes, facilitating the occurrence of dipole polarization. Consequently, the developed dual-phase high-entropy sulfide exhibited outstanding microwave absorption properties. The minimum reflection loss value of (FeCoNiCuZn)S was -45.8 dB at a thickness of 1.5 mm, and the optimal effective absorption bandwidth was 3.8 GHz at a thickness of 1.4 mm thickness. Thus, the design of high-entropy sulfides brings meaningful guidance for tuning the wave absorption properties in sulfides.

Fluorinated bamboo-structure carbon nanotubes: as attractive substrates for the cathodes of lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries have gained considerable attention for high theoretical specific capacity and energy density. However, their development is hampered by the poor electrical conductivity of sulfur and the shuttle of polysulfides. Herein, the acidified bamboo-structure carbon nanotubes (BCNTs) were mixed with polyvinylidene difluoride and pyrolyzed at high-temperature to obtain the fluorinated bamboo-structure carbon nanotubes (FBCNTs), which were compounded with sulfur as the cathode. The prepared S@FBCNTs with sulfur loading reaching 74.2 wt.% shows a high initial specific capacity of 1407.5 mAh·g−1 at the discharge rate of 0.1 C. When the discharge rate was increased to 5 C, the capacity could be maintained at 622.3 mAh·g−1. The electrical conductivity of carbon nanotubes is effectively improved by semi-ionic C–F bonds formed by the doped F atoms and carbon atoms. Simultaneously, the surface of the F-containing carbon tubes exhibits strong polarity and strong chemisorption effect on polysulfides, which inhibits the shuttle effect of Li–S batteries.

Exceptionally Bifunctional ORR/OER Performance via Synergistic Atom-Cluster Interaction.

The single-atom sites (SAs) have achieved enhanced performance toward oxygen reduction reaction (ORR) with the effective utilization of the active sites. However, the excess adsorption of the intermediates and the limited stability hinders performance improvement. Metal clusters with promising stability and weak adsorption can be used as potential substitutions, but the lack of active sites is considered undesirable for catalytic reactions. Herein, a framework of Fe nanoclusters combined with SAs on One dimensional (1D)carbon nanotubes (Fe3C-NCNTs 90minCC-1) is synthesized to confirm the synergistic atom-cluster interaction. The composite exhibits strong polarization and electron redistribution between nanocluster and SAs. The electron redistribution will significantly boost the electron transport and the desorption of the intermediates, which is confirmed by off-axis holography and DFT calculation. The electrocatalytic performance is significantly enhanced as the half-wave potential of ORR increased 75mV and the potential of OER increased 133mV compared with the sample without nanoclusters. Furthermore, such a bifunctional catalyst endows homemade Zn-air batteries (ZABs) with high power density and long-term stability. This work paves a facile route to design bifunctional ORR/OER electrocatalysts consisting of 0D composite structures.

Applications, prospects and challenges of metal borides in lithium sulfur batteries

Although the lithium-sulfur (Li-S) battery has a theoretical capacity of up to 1675 mA h g−1, its practical application is limited owing to some problems, such as the shuttle effect of soluble lithium polysulfides (LiPSs) and the growth of Li dendrites. It has been verified that some transition metal compounds exhibit strong polarity, good chemical adsorption and high electrocatalytic activities, which are beneficial for the rapid conversion of intermediate product in order to effectively inhibit the “shuttle effect”. Remarkably, being different from other metal compounds, it is a significant characteristic that both metal and boron atoms of transition metal borides (TMBs) can bind to LiPSs, which have shown great potential in recent years. Here, for the first time, almost all existing studies on TMBs employed in Li-S cells are comprehensively summarized. We firstly clarify special structures and electronic features of metal borides to show their great potential, and then existing strategies to improve the electrochemical properties of TMBs are summarized and discussed in the focus sections, such as carbon-matrix construction, morphology control, heteroatomic doping, heterostructure formation, phase engineering, preparation techniques. Finally, the remaining challenges and perspectives are proposed to point out a direction for realizing high-energy and long-life Li-S batteries.

Study on inherent characteristics of asphalt regenerating agents: Insights from density functional theory calculations and molecular dynamics simulations

The asphalt mixtures containing reclaimed asphalt pavement (RAP) are gradually used in pavement. When the RAP content exceeds 25%, the influence of RAP properties on the performance of the asphalt mixture becomes more pronounced. To address this barrier, the incorporation of regenerating agents is adopted to soften RAP asphalt and ensure the performance of the asphalt mixture. Currently, research on the effect of regenerating agents is rapidly advancing, but there remains limited exploration of their inherent characteristics. This study employs advanced tools such as molecular dynamics (MD) simulations and density functional theory (DFT) to investigate the chemical properties and material attributes of regenerating agents. Fourteen common regenerating agents are selected, which can be classified into eight categories (A∼H) based on their structural features. The results reveal that linear alkanes and cycloalkanes are nonpolar surfaces due to their inherent structural characteristics, resulting in larger fraction free volume (FFV) values within the molecular structure. Considering the molecular weight and intermolecular interactions, these components exhibit a higher diffusion coefficient (D) value. In contrast, aromatics with benzene rings experience enhanced polarity and intermolecular interaction due to conjugated electron pairs forming π-π interactions, leading to reduced FFV values and D values. Moreover, the increase in molecular weight of aromatics significantly reduces both intermolecular interactions and D values. The carboxyl group in fatty acids leads to higher polarity, resulting in stronger intermolecular interactions and lower FFV values and D values. However, after esterification, the properties of fatty acid esters show improvement. Glycerol, with its hydroxyl group having the strongest polarity, exhibits a dense arrangement with the highest density and solubility parameters, which may exceed that of asphalt and may not be suitable as a rejuvenator. The investigation reveals that the polarity of regenerating agents is positively correlated with density, cohesive energy density, and solubility parameters.

Constructing Multiphase-Induced Interfacial Polarization to Surpass Defect-Induced Polarization in Multielement Sulfide Absorbers.

The extremely weak heterointerface construction of high-entropy materials (HEM) hinders them being the electromagnetic wave (EMW) absorbers with ideal properties. To address this issue, this study proposes multiphase interfacial engineering and results in a multiphase-induced interfacial polarization loss in multielement sulfides. Through the selection of atoms with diverse reaction activities, the multiphase interfacial components of CuS (1 0 5), Fe0.5 Ni0.5 S2 (2 1 0), and CuFe2 S3 (2 0 0) are constructed to enhance the interfacial polarization loss in multielement Cu-based sulfides. Compared with single-phase high-entropy Zn-based sulfides (ZnFeCoNiCr-S), the multiphase Cu-based sulfides (CuFeCoNiCr-S) possess optimized EMW absorption properties (effective absorption bandwidth (EAB) of 6.70GHz at 2.00mm) due to the existence of specific interface of CuS (1 0 5)/CuFe2 S3 (2 0 0) with proper EM parameters. Furthermore, single-phase ZnFeCoNiCr-S into FeNi2 S4 (3 1 1)/(Zn, Fe)S (1 1 1) heterointerface through 400°C heat-treated is decomposed. The EMW absorption properties are enhanced by strong interfacial polarization (EAB of 4.83GHz at 1.45mm). This work reveals the reasons for the limited EMW absorption properties of high-entropy sulfides and proposes multiphase interface engineering to improve charge accumulation and polarization between specific interfaces, leading to the enhanced EMW absorption properties.

Unveiling the sp2 ─sp3 C─C Polar Bond Induced Electromagnetic Responding Behaviors by a 2D N-doped Carbon Nanosheet Absorber.

The infertile electromagnetic (EM) attenuating behavior of carbon material makes the improvement of its performance remain a significant challenge. Herein, a facile and low-cost strategy radically distinct from the prevalent approaches by constructing polar covalent bonds between sp2 -hybridized and sp3 -hybridized carbon atoms to introduce strong dipolar polarization is proposed. Through customizing and selectively engineering the N moieties conjugated with carbon rings, the microstructure of the as-synthesized 2D nanosheet is gradually converted with the partial transition from sp3 carbons to sp2 carbons, where the electric dipoles between them are also tuned. Supported by the DFT calculations, a progressively enhanced sp2 ─sp3 C─C dipolar polarization is caused by this controllable structure evolution, which is demonstrated to contribute dominantly to the total dielectric loss. By virtue of this unduplicated loss behavior, a remarkable effective absorption bandwidth (EAB) beyond -10dB of 8.28GHz (2.33mm) and an ultrawide EAB beyond -5dB of 13.72GHz (4.93mm) are delivered, which upgrade the EM performance of carbon material to a higher level. This study not only demonstrates the huge perspective of sp2 ─sp3 -hybridized carbon in EM elimination but also gives pioneering insights into the carbon-carbon polarization mechanism for guiding the development of advanced EM absorption materials.

Defects-rich TiO2(B) in-situ grown on carbon fiber cloth as self-standing electrode for high-loading lithium–sulfur batteries

Poor conductivity, severe shuttling of soluble lithium polysulfides (LiPSs), and sluggish sulfur redox kinetics are inherent issues existing in lithium-sulfur batteries (LSBs). Herein, a self-standing electrode was designed and constructed via the in-situ growth of defects-rich TiO2(B) on a carbon cloth (CC) (denoted as TiO2-x(B)@CC). The strong polarity and high electrochemical activity of TiO2-x(B) enables strong chemical adsorption for LiPSs and catalyzes sulfur conversion reactions. CC as growth substrate inhibits the agglomeration of TiO2-x(B) nanosheets and improves electrical conductivity, as well as holds high sulfur loadings. Benefiting from these synergistic effects, TiO2-x(B)@CC-based cathode with a sulfur loading of ∼ 2.5 mgS cm−2 maintained a high specific capacity of 500 mAh/g over 200cycles at 2.0C. Even under high sulfur loading of ∼ 8.1 mgS cm−2 and a low electrolyte/sulfur (E/S) ratio of ∼ 6.5 μL mgS-1, it still achieved good rate capacities.

Interband transition physics from the absorption edge in GaN: New prospects from numerical analysis

The strong polarization effects and abundant surface states in III-nitrides result in a tunable electric field, modifying the absorption/emission by changing the band structure. Thus, the mechanism of the electric field and the absorption/emission is crucial for future optical logic devices. Here, we propose to extract the information from the absorption/emission edge by numerical simulations. The simulations show that the increase in the field strength would red-shift the spectrum as well as decrease the slope of the edge for both the uniform and non-uniform field. For numerical simulations, we also provide the lower limit of the quantum states to be simulated from Wentzel–Kramers–Brillouin approximation. Then three GaN samples with different n values are analyzed, and the results validate our methods in two ways. On the one hand, the nonuniform field is shown to fit the experimental absorption better at higher n, which is in accordance with previous studies. On the other hand, the reasonable bandgap Eg at zero doping level and the bandgap-renormalization coefficient are obtained. This work would deepen the understanding of the absorption/emission influenced by the electric field and pave the way for numerical analysis of the edge.

3D porous NiCo2(CO3)3/reduced graphene oxide aerogel with heterogeneous interfaces for high-efficiency microwave absorption

Advanced electromagnetic absorbing materials (EAMs) with strong absorption and a wide effective absorption bandwidth (EAB), using innovative microstructural design and suitable multicomponents remain a persistent challenge. Here, we report the production of a material by the hydrothermal reduction of a mixture of graphene oxide (GO), Ni(NO3)2·6H2O, and Co(NO3)2·6H2O, resulting in reduced GO (RGO) with a self-assembled 3D mesh structure filled with NiCo2(CO3)3. The unique microstructure of this assembly not only solves the problem of NiCo2(CO3)3 particles agglomerating but also changes the electromagnetic parameters, thereby improving the impedance matching and attenuation ability. High electromagnetic wave absorption (EMA) was achieved by combining the 3D interconnected mesh structure and the various interfaces between NiCo2(CO3)3 and RGO. The minimal reflection loss (RLmin) was −58.5 dB at 2.3 mm, and the EAB was 6.5 GHz. The excellent EMA performance of the aerogel can be attributed to the multiple reflection, scattering, and relaxation process of the porous 3D structure as well as the strong polarization of the interfacial matrix.

High-performance van der Waals antiferroelectric CuCrP2S6-based memristors

Layered thio- and seleno-phosphate ferroelectrics, such as CuInP2S6, are promising building blocks for next-generation nonvolatile memory devices. However, because of the low Curie point, the CuInP2S6-based memory devices suffer from poor thermal stability (<42 °C). Here, exploiting the electric field-driven phase transition in the rarely studied antiferroelectric CuCrP2S6 crystals, we develop a nonvolatile memristor showing a sizable resistive-switching ratio of ~ 1000, high switching endurance up to 20,000 cycles, low cycle-to-cycle variation, and robust thermal stability up to 120 °C. The resistive switching is attributed to the ferroelectric polarization-modulated thermal emission accompanied by the Fowler–Nordheim tunneling across the interfaces. First-principles calculations reveal that the good device performances are associated with the exceptionally strong ferroelectric polarization in CuCrP2S6 crystal. Furthermore, the typical biological synaptic learning rules, such as long-term potentiation/depression and spike amplitude/spike time-dependent plasticity, are also demonstrated. The results highlight the great application potential of van der Waals antiferroelectrics in high-performance synaptic devices for neuromorphic computing.

Too Lucky To Be True: Fairness Views under the Shadow of Cheating

Abstract Income inequalities within societies are often associated with evidence that the rich are more likely to behave unethically and evade more taxes. We study how fairness views and preferences for redistribution are affected when cheating may, but need not, be the cause of income inequalities. In our experiment, we let third parties redistribute income between a rich and a poor stakeholder. In one treatment, income inequality was only due to luck, while in two others rich stakeholders might have cheated. The mere suspicion of cheating changes third parties' fairness views considerably and leads to a strong polarization that is even more pronounced when cheating generates negative externalities.

Achieving long-term stable BiVO4 photoanodes for solar water splitting via carbon-layer protecting combined with active centers dynamic repairing

Although great interest is focused on highly active photoanodes for efficient photoelectrochemical (PEC) water splitting, the issue on improving stability during oxygen evolution reaction (OER) is seldom discussed by far. Herein, a simple chemical way to construct carbon functional interlayer between bismuth vanadate (BiVO4) and NiFe layered double hydroxide (NiFe-LDH) co-catalyst, combined with hydroxylation, can significantly improve the activity and stability. The enhanced electronic conductivity by carbon layer and formed strong polarization electronic field via surface hydroxylation, promote the interfacial charge transfer and bulk charge separation. More importantly, the carbon layer combined with more efficient redeposition of Fe active centers in NiFe-LDH catalysts caused by enhanced adsorption of Fe(III) onto Ni sites via hydroxylation, can greatly improve the OH-BiVO4@C@NiFe-LDH photoanode stability. With the synergistic effects of carbon functional interlayer and self-healing mechanism, OH-BiVO4@C@NiFe-LDH photoanode achieves extremely high photocurrent density (5.31 mA cm−2 at 1.23 versus the RHE), even maintaining more than 87.5 % of the initial photocurrent density within 20 h irradiation in KBi electrolyte with Fe(III) ions. This work provides a new strategy to enhance the performance of BiVO4–based photoanodes, especially for achieving long-term stability during OER.

Atomic Zincophilic Sites Regulating Microspace Electric Fields for Dendrite-Free Zinc Anode.

Aqueous Zn metal batteries are promising candidates for large-scale energy storage due to their intrinsic advantages. However, Zn tends to deposit irregularly and forms dendrites driven by the uneven space electric field distribution near the Zn-electrolyte interphase. Herein it is demonstrated that trace addition of Co single atom anchored carbon (denoted as CoSA/C) in the electrolyte regulates the microspace electric field at the Zn-electrolyte interphase and unifies Zn deposition. Through preferential adsorption of CoSA/C on the Zn surface, the atomically dispersed Co-N3 with strong charge polarization effect can redistribute the local space electric field and regulate ion flux. Moreover, the dynamic adsorption/desorption of CoSA/C upon plating/stripping offers sustainable long-term regulation. Therefore, Zn||Zn symmetric cells with CoSA/C electrolyte additive deliver stable cycling up to 1600h (corresponding to a cumulative plated capacity of 8 Ah cm-2 ) at a high current density of 10mA cm-2 , demonstrating the sustainable feature of microspace electric field regulation at high current density and capacity.