Polarization Coupling Research Articles

Spin Hall effect induced by strain coupling of valley and spin polarization in puckered monochalcogenide tellurene monolayer

Spin Hall effect induced by strain coupling of valley and spin polarization in puckered monochalcogenide tellurene monolayer

Effects of electrostatic coupling and surface polarization on polyelectrolyte brush structure.

In this work, we perform molecular dynamics simulations to study a spherical polyelectrolyte brush. We explore the effects of surface polarization and electrostatic coupling on brush size and distribution of counterions. The method of image charges is considered to take into account surface polarization, considering a metallic, an unpolarizable, and a dielectric nano-core. It is observed that, for all cases, a moderate shrinking-swelling effect appears with an increase in the electrostatic coupling parameter. This effect occurs under high Manning ratios. The curves relating the average size of polyelectrolyte brush as a function of coupling show a minimum. The results show that the grafting density of polyelectrolytes on the nano-core surface plays an important role in the polarization effect. We consider a modified Poisson-Boltzmann theory to describe the counterion profiles around the brush in the case of unpolarizable nano-cores and weak electrostatic coupling.

High-pressure single crystal growth and magnetoelectric properties of CdMn7O12

The concurrent presence of large electric polarization and strong magnetoelectric coupling is quite desirable for potential applications of multiferroics. In this paper, we report the growth of CdMn7O12 single crystals by flux method under a high pressure of 8 GPa for the first time. An antiferromagnetic (AFM) order with a polar magnetic point group is found to occur at the onset temperature of T N1 = 88 K (AFM1 phase). As a consequence, the pyroelectric current emerges at T N1 and gradually increases and reaches its maximum at T set = 63 K, at which the AFM1 phase finally settles down. Below T set, CdMn7O12 single crystal exhibits a large ferroelectric polarization up to 2640 µC m−2. Moreover, the spin-induced electric polarization can be readily tuned by applying magnetic fields, giving rise to considerable magnetoelectric coupling effects. Thus, the current CdMn7O12 single crystal acts as a rare multiferroic system where both large polarization and strong magnetoelectric coupling merge concurrently.

Controlling Displacement Fields in Polar Willis Solids via Gauge Transformations.

Rigid-body displacement and deformation constitute the total displacement field of a solid. Harnessing the former calls for well-organized kinematic elements, and controlling the latter allows for creation of shape-morphing materials. A solid capable of simultaneously controlling both rigid-body displacement and deformation remains unknown. Here, we exploit gauge transformations to show how the total displacement field in elastostatic polar Willis solids can be harnessed at will and how those solids can be realized in the form of lattice metamaterials. The transformation method we develop leverages a displacement gauge in linear transformation elasticity, giving rise to polarity and Willis coupling such that the resulting solids not only break minor symmetries of the stiffness tensor, but display cross coupling between stress and displacement. We realize those solids using a combination of tailored geometries, grounded springs, and a set of coupled gears and numerically demonstrate a range of satisfactory, and peculiar, displacement control functions. Our work provides an analytical framework for the inverse design of grounded polar Willis metamaterials to achieve arbitrary displacement control functions by design.

Light-Controlled Magnetoelastic Effects in Ni/BaTiO3 Heterostructures

Magnetoelastic and magnetoelectric coupling in the artificial multiferroic heterostructures facilitate valuable features for device applications such as magnetic field sensors and electric-write magnetic-read memory devices. In ferromagnetic/ferroelectric heterostructures, the intertwined physical properties can be manipulated by an external perturbation, such as an electric field, temperature, or a magnetic field. Here, we demonstrate the remote-controlled tunability of these effects under visible, coherent, and polarized light. The combined surface and bulk magnetic study of domain-correlated Ni/BaTiO3 heterostructures reveals that the system shows strong sensitivity to the light illumination via the combined effect of piezoelectricity, ferroelectric polarization, spin imbalance, magnetostriction, and magnetoelectric coupling. A well-defined ferroelastic domain structure is fully transferred from a ferroelectric substrate to the magnetostrictive layer via interface strain transfer. The visible light illumination is used to manipulate the original ferromagnetic microstructure by the light-induced domain wall motion in ferroelectric substrates and consequently the domain wall motion in the ferromagnetic layer. Our findings mimic the attractive remote-controlled ferroelectric random-access memory write and magnetic random-access memory read application scenarios, hence facilitating a perspective for room temperature spintronic device applications.

Spatial characteristics and coupling coordination between carbon emission efficiency and industrial structure in three metropolitan areas of Jiangsu Province, China.

It is of great practical significance to study the spatial characteristics of carbon emission efficiency, industrial structure, their coupling and coordination relationship for China's green development and industrial structure transformation in the new era. From the perspective of coupling, coordination and space, this paper analyzes and summarizes the spatial characteristics of carbon emission efficiency and industrial structure of 19 cities in three metropolitan areas of Jiangsu Province during 2009-2019 and their coupling and coordination relationship. The carbon emission efficiency in this study is represented by the carbon emission economic efficiency index and carbon emission social efficiency index. The results show that (a) the high-emission centers in the three metropolitan areas developed from "three centers" in 2009 to "five centers" in 2019. The continuous high-energy consumption of the secondary industry and the growth of the economic aggregate of the third industry kept the regional high carbon dioxide emissions. (b) The average value of carbon emission economic efficiency in 19 cities continued to increase, indicating that the contribution rate of the same amount of carbon emissions to economic income gradually increased; the growth range of carbon emission economic efficiency index is greater than that of carbon emission social efficiency index, indicating that carbon emission has a more significant effect on the improvement of regional economic development than on the improvement of public service level and residents' living quality. (d) The solidification degree of carbon emission efficiency is greater than that of the industrial structure (solidification degree carbon emission social efficiency > carbon emission economic efficiency > industrial structure). The high-grade industrial structure in Xuzhou metropolitan area is closely related to the improvement of carbon emission economic efficiency and carbon emission social efficiency, and both are in moderate antagonism. The rationalizing industrial structure in Nanjing metropolitan area is closely related to the improvement of carbon emission economic efficiency, which is in high coordination run-in. The concentration degree of industrial structure in Suzhou-Wuxi-Changzhou metropolitan area is closely related to the improvement of carbon emission economic efficiency and carbon emission social efficiency, which are in polar coordination coupling and high coordination run-in, respectively. The proposed coupling path of carbon emission efficiency-industrial structure can not only alleviate the dynamic disharmony in different cities but also effectively improve the coupling degree in cities.

Current-induced spin polarization in Janus WSSe monolayer

Janus engineering of transition metal dichalcogenide monolayers breaks the vertical mirror symmetry and induces huge built-in polarization and large Rashba spin-orbit coupling. By performing first-principles calculations, we find that the Rashba spin-orbit coupling induces sizable current-induced spin polarization in both the conduction and valence bands in the Janus WSSe monolayer, which is comparable to that in perovskite oxide interfaces. By constructing the low-energy $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ Hamiltonian from the invariant theory, we find a sign change of the current-spin conductivity at chemical potential $\ensuremath{\mu}\ensuremath{\approx}\ensuremath{-}0.73$ eV, which indicates the flip of spin polarization and is attributed to the competition between the intrinsic Rashba spin-orbit coupling and the hexagonal warping of the valence bands. Our numerical and analytic results suggest that the current-induced spin polarization in the Janus WSSe monolayer is insensitive to temperature and impurity concentration but can be effectively tuned by external biaxial or uniaxial strain. The Janus WSSe monolayer could be a promising candidate to realize flexible two-dimensional spintronics devices.

Core-shell structure and domain engineering in Bi0.5Na0.5TiO3-based ceramics with enhanced dielectric and energy storage performance

Core–shell structured Bi0.5Na0.5TiO3KTaO3 + x% (in mass) Li2CO3 ceramics were fabricated in this study. Increasing x from 0 to 2 leads to the decrease of sintering temperature from 1 175 °C to 1 020 °C. The limited diffusion of Ta5+ results in chemical heterogeneities and core–shell microstructures. The Ta5+-depleted cores show the nanodomains (∼10 nm), while the Ta5+-rich shells display the polar nanoregions (1–2 nm). From x = 0 to 1, the appearance of cores with nanodomains contributes to the increase of dielectric constant and maximum polarization, while the further addition of Li2CO3 suppresses the dielectric and polarization responses due to the reduced grain sizes and polarization coupling. The enhanced dielectric relaxation and existence of core-shell microstructure with different polarization levels help to optimize the dielectric temperature stability. The x = 2 ceramics exhibit a stable high dielectric constant ∼1 400 over a wide temperature range of 20–520 °C. More encouragingly, the ultrafine grain size and core–shell microstructure in the x = 2 ceramics greatly benefit the improvement of breakdown strength. Combined with the delayed polarization saturation and high ergodicity, a high recoverable energy density of ∼5.07 J/cm3 is obtained under 44 kV/mm, with a high efficiency of ∼85.17%.

Dual polarization and mutual coupling improvement of UWB MIMO antenna with cross shape decoupling structure

A simple, compact MIMO antenna that operates in the UWB frequency band is presented in this paper. The proposed antenna consists of four elements where the shape of the radiators derived from series modifications of a conventional rectangular patch antenna. Radiators are placed orthogonally to each other to achieve the dual polarization operation and cross shape Defected Ground Structure (DGS) is inserted in the ground plane to improve decoupling between the antenna elements. The designed model was fabricated on FR-4 substrate with dimensions of 48 × 44 × 1.6 mm3 and measurements were performed to validate the simulated results. The fractional bandwidth reaches 112% from 3.1 GHz to 11 GHz with reflection coefficient less than -10 dB and mutual coupling between antenna elements is less than -20 dB. The antenna has a stable radiation pattern, and low gain variation. In addition, the time domain characteristics and diversity performance indicators were evaluated and compared with the standard values. The miniaturized dimensioning of the antenna along with the good performance metrics indicates that the proposed antenna can be used in various UWB applications such as portable handheld devices.

Polarization and orbital angular momentum coupling for high-dimensional measurement-device-independent quantum key distribution protocol

Polarization and orbital angular momentum coupling for high-dimensional measurement-device-independent quantum key distribution protocol

Ferroelectric polarization and interface engineering coupling of Z-scheme ZnIn2S4/α-In2Se3 heterostructure for efficient photocatalytic water splitting

It is of great significance to design an efficient heterostructure for photocatalytic hydrogen production to solve the energy shortage and environmental crisis. In this letter, we investigate the structure, electron of interface, optical, charge transfer, and photocatalytic mechanism of three different ZnIn2S4/α-In2Se3 heterostructures by hybrid density functional calculation. It is interesting that the presence of an external electric field not only can change the bandgap but also can modulate the band alignment type. Among them, heterostructure A belongs to type II heterostructure, and heterostructure B and C belong to a Z-scheme heterostructure. Especially in heterostructure C, the electrons deposited on CBM of a ZnIn2S4 monolayer will play an important role in the hydrogen production process. Meanwhile, the small bandgap of ZnIn2S4/α-In2Se3 Z-scheme heterostructures enables it to obtain a wide light absorption range. Therefore, this study contributes to the design of a novel and potential Z-scheme heterostructure photocatalyst with broad application prospects in both electronic and optoelectronic fields.

Critical splay fluctuations and colossal flexoelectric effect above the nonpolar to polar nematic phase transition

The recent discovery of nematic liquid crystals with polar order (ferroelectric) has created immense interest. Despite intensive research, several physical properties of this liquid crystal are yet to be investigated and understood. Here, we report experimental studies on the surface alignment, birefringence, and flexoelectric coefficient of a polar nematic $({N}_{\mathrm{F}})$ liquid crystal. Our experiments directly reveal that the splay fluctuations influence the birefringence several degrees above the nonpolar $(N)$ to polar nematic $({N}_{\mathrm{F}})$ phase transition temperature, and the heat capacity exponent obtained from the tilt angle fluctuations is close to the value reported in adiabatic scanning calorimetry measurements. The flexoelectric coefficient of the nonpolar nematic phase shows a power-law dependence on temperature. It demonstrates a strong polar coupling of pretransitional ferroelectric fluctuations with the field. These results are important for applications as well as for understanding all pretransitional effects in ferroelectric nematic liquid crystals.

Fully epitaxial, monolithic ScAlN/AlGaN/GaN ferroelectric HEMT

In this Letter, we demonstrated fully epitaxial ScAlN/AlGaN/GaN based ferroelectric high electron mobility transistors (HEMTs). Clean and atomically sharp heterostructure interfaces were obtained by utilizing molecular beam epitaxy. The fabricated ferroelectric gate HEMTs showed counterclockwise hysteretic transfer curves with a wide threshold voltage tuning range of 3.8 V, a large ON/OFF ratio of 3 × 107, and reconfigurable output characteristics depending on the poling conditions. The high quality ferroelectric gate stack and effective ferroelectric polarization coupling lead to improved subthreshold performance, with subthreshold swing values approaching 110 and 30 mV/dec under forward and backward gate sweeps, respectively. The results provide fundamental insight into the ferroelectric polarization coupling and threshold tuning processes in ferroelectric nitride heterostructures and are promising for nitride-based nonvolatile, multi-functional, reconfigurable power, and radio frequency devices as well as memory devices and negative capacitance transistors for next-generation electronics.

The Effects of Humidity on Dielectric Permittivity of Surface-Modified TiO₂- and MgO-Based Polypropylene Nanocomposites

This work reports on the effects of titanium dioxide (TiO2) and magnesium oxide (MgO) nanofillers modified with polar silane coupling agents (SCAs) on the dielectric response of polypropylene (PP) nanocomposites, in the presence of water molecules. A thermogravimetric analysis (TGA) demonstrates that the surface structure of the SCA layer between TiO2 and MgO is significantly different, since the SCA graft density of MgO is ten times higher than for TiO2. Surface-modified nanofillers tend to agglomerate, and that the distribution is determined by the polarity of the surface functional groups. Agglomerations in methacrylate systems are similar in size to those found in untreated samples (3– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5~\mu \text{m}$ </tex-math></inline-formula> ), while those with amino functional groups are reduced to 1– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2~\mu \text{m}$ </tex-math></inline-formula> . Nanoparticles also act as nucleating agents, which increases the crystallization temperature by 7 °C–8 °C compared with neat PP. The measured increase in relative permittivity in the composites is attributed to absorbed water. Surface modification significantly reduces this increase, especially in MgO samples. Relaxation peak frequencies vary, depending on the water bonding states, due to differences in polarities of the respective surface functional groups. Two overlapping dielectric mechanisms of dipolar and interfacial relaxation can be detected, especially at low frequencies (LFs; 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Hz) in TiO2 samples. Ethoxy-modified samples containing amino functional groups have the lowest dielectric permittivity under humid conditions.

Orbital-Angular-Momentum Quantum State Transformation Via a Nonlinear Process

Orbital-angular-momentum- (OAM) based photonic nonlinear interfaces, such as the nonlinear manipulation of a single-photon OAM state between the communication wavelength for entanglement distribution and the near-visible wavelength for quantum memories. Here, we experimentally demonstrate this kind of quantum state transformation for simultaneously adjusting the weight of the spatial OAM modes and operating the wavelength of single photons by effectively cascading the frequency conversion and electro-optical (EO) polarization coupling in a periodically poled lithium niobate crystal. The fidelity of the OAM state is measured to be higher than 95% before and after the frequency conversion. The results show that the OAM state of single photons can be modulated on demand by applying a transverse electric field across the nonlinear crystal. Our work demonstrates the integration and high performance of our proposed transformation interface, and paves a route toward connecting different remote nodes based on quantum memories in a large-scale OAM-encoded quantum network.

Experimental demonstration of TE/TM polarization-independent frequency upconversion assisted by polarization coupling

Experimental demonstration of TE/TM polarization-independent frequency upconversion assisted by polarization coupling

The intermolecular polar bond interaction and coupling induced spectral splitting phenomenon for a binary mixture.

To explain the polarization Raman noncoincidence effect of specific polar bonds and the noncoincidence phenomenon between FT-Raman and FT-IR spectra, aggregation-induced spectral splitting theory was proposed. In this paper, the vibration splitting theory was demonstrated using two strategies: improving the spectral resolution with cryogenic matrix isolation techniques and identifying cases where the coupling splitting is large enough to be distinguishable. The monomer and dimer splitting bands of acetone were detected when cryogenically isolated by the Ar matrix. Additionally, the polarization Raman and two-dimensional infrared spectra of a β-propiolactone (PIL)/CCl4 binary mixture were collected at room temperature, and the spectral splitting phenomenon was clearly observed. The dynamic transformation between the monomer and dimer could be achieved and detected by adjusting the PIL concentration. The observed splitting phenomenon was further confirmed by theoretical DFT calculations based on the monomer and dimer of PIL, as well as the FT-IR and FT-Raman spectra of PIL. Concentration-triggered 2D-COS synchronous and asynchronous spectra also confirmed the splitting phenomenon and the dilution kinetics of PIL/CCl4.

Combined piezoelectricity, valley splitting and Dzyaloshinskii-Moriya interaction in Janus GdXY (X, Y = Cl, Br, I) magnetic semiconductors.

Janus materials, as a family of multifunctional materials with broken mirror symmetry, have played a great role in piezoelectric, valley-related, and Rashba spin-orbit coupling (SOC) applications. Using first-principles calculations, it is predicted that monolayer 2H-GdXY (X, Y = Cl, Br, I) will combine giant piezoelectricity, intrinsic valley splitting and a strong Dzyaloshinskii-Moriya interaction (DMI), resulting from the intrinsic electric polarization, spontaneous spin polarization and strong spin-orbit coupling. Opposite Berry curvatures and unequal Hall conductivities at the K- and K'-valleys of monolayer GdXY are promising for storing information through the anomalous valley Hall effect (AVHE). Through construction of the spin Hamiltonian and micromagnetic model, we obtained the primary magnetic parameters of monolayer GdXY as a function of the biaxial strain. Due to the dimensionless parameter κ having strong tunability, monolayer GdClBr is promising to host isolated skyrmions. The present results are expected to enable the application of Janus materials in piezoelectricity, spin- and valley-tronics and the formation of chiral magnetic structures.

Facile synthesis of heterogeneous Co/MnO@C nanocapsules with dual-cores: Achieving strong and broadband microwave absorption by magnetic-dielectric synergy

Nowadays, constructing a high-efficiency microwave absorber with strong absorption strength and wide absorption bandwidth is urgently demanded for practical applications in the microwave absorption (MA) field. In this work, the Co/MnO@C nanocapsules with magnetic/dielectric dual cores were fabricated through in-situ carbon reduction of the MnCo2O4 nanoparticles. The effects of calcination temperature on electromagnetic parameters and MA ability are investigated in detail. Notably, the sample obtained at 900 ℃ exhibits the minimum reflection loss (RL) value of −97.5 dB at 10.6 GHz, while the effective absorption bandwidth (EAB, RL ≤ −10 dB) is up to 8.1 GHz (9.9–18 GHz) at 2.1 mm thickness, covering half of X-band and whole Ku-band. The excellent MA performance is attributed to the core–shell structure, multiple heterogeneous interface polarizations, synergistic effects between magnetic and dielectric components, as well as promoted impedance matching. Importantly, the electric and magnetic field distributions are simulated by ANSYS software, and the polarization and magnetic coupling behaviors are deeply analyzed. The simulated radar cross-section (RCS) results confirm that the optimized Co/MnO@C nanocapsules can efficaciously attenuate more electromagnetic energy in the practical environment. It is believed that the as-prepared Co/MnO@C nanocapsules are considered to be promising high-efficiency microwave absorbers for practical applications.

On the strong coupling of polarization and charge trapping in HfO2/Si-based ferroelectric field-effect transistors: overview of device operation and reliability

On the strong coupling of polarization and charge trapping in HfO2/Si-based ferroelectric field-effect transistors: overview of device operation and reliability