Coexistence Of States Research Articles

Enhanced magnetic transition temperature through ferromagnetic and antiferromagnetic interaction in cobalt-substituted Fe5GeTe2

Two-dimensional (2D) magnetism is an incredibly intriguing phenomenon in condensed matter physics. The exploration of 2D magnets holds great promise for various applications, even though they often exhibit low magnetic transition temperature. Among these materials, Fe5GeTe2 has emerged as a compelling candidate for room-temperature spintronics due to its intrinsic ferromagnetism and high Curie temperature. In this study, we investigate the impact of Co substitution at the Fe sites in Fe5GeTe2, which induces a transition of the magnetic ground state to the antiferromagnetic state when the substitution level exceeds 0.36. Additionally, we observe the coexistence of ferromagnetic (FM) and antiferromagnetic states in the magnetic transition region of (Fe1−xCox)5GeTe2 crystals. Notably, the interaction between the two magnetic phases results in Néel temperature (TN) up to 374 K, establishing a record among known van der Waals antiferromagnets. Our findings present a strategy for enhancing the magnetic temperature of 2D magnets, paving the way for potential advancements in spintronics applications.

A dynamic analysis of capital, corruption, and labor market interactions

The complex relationship between corruption, economic growth, and labor dynamics has long been a challenge for policymakers. This study sheds new light on these dynamic interactions by constructing a novel economic model with saturation effects that integrate employment considerations. Unlike static or purely empirical models, our approach captures the system’s evolution over time, employing a logistic growth function to realistically reflect economic limitations and distinguishing between employed and unemployed labor segments. By incorporating a Holling type II function, the model captures the nonlinear influence of corruption on economic growth, acknowledging diminishing returns at higher corruption levels. Through advanced theoretical analysis, we establish the existence and stability conditions for three distinct long-term equilibria: stagnation, corruption-free growth with full employment, and a coexistent state where corruption persists alongside some economic activity. Our analysis goes beyond merely identifying these equilibria by revealing the specific conditions under which each state prevails, and we solidify these theoretical predictions with comprehensive numerical simulations depicting the system’s behavior under varying conditions. The findings underscore the importance of robust anti-corruption measures and a labor-intensive economic approach, highlighting that fostering growth outpacing resource depletion is crucial for escaping stagnation and achieving sustainable development. Overall, this research advances the field by integrating employment dynamics, a Holling type II function for corruption, and a focus on stability analysis, providing invaluable insights for policymakers aiming to promote sustainable economic development, combat corruption, and ensure healthy employment conditions.

Dynamics of reaction–diffusion–advection system and its impact on river ecology in the presence of spatial heterogeneity

This study considers a two-species reaction–diffusion–advection (RDA) model in a heterogeneous advective environment with zero Neumann boundary conditions. We suppose that two species compete for the same food resource but have different diffusion and advection rates. The primary objective of this study is to investigate the global asymptotic stability and coexistence of steady state based on different and unequal diffusion and advection rates through theoretical and numerical analysis. We establish the local stability of two semi-trivial steady states of the competing species. Also, the non-existence of coexistence steady state is proved with the help of some non-trivial assumptions. Finally, we show the global stability with the help of monotone dynamical systems and combine the local stability and non-existence of coexistence steady state. If one species adopts a smaller diffusion and advection rate, the competition’s result depends on the advection and diffusion rate ratio. If the ratio is smaller, then the species will prevail. Also, the species with higher diffusion and smaller advection will win. Lastly, the effectiveness of the model in one and two-dimensional situations is shown by a series of numerical calculations, which is particularly important for environmental consideration.

Anomalous Fraunhofer-like patterns in quantum anomalous Hall Josephson junctions

The intriguing interplay between topology and superconductivity has attracted significant attention, given its potential for realizing topological superconductivity. In the quantum anomalous Hall insulators (QAHIs)-based junction, the supercurrents are carried by the chiral edge states, characterized by a 2Φ0 magnetic flux periodicity (Φ0=h/2e is the flux quantum, h the Planck constant, and e the electron charge). However, experimental observations indicate the presence of bulk carriers in QAHI samples due to magnetic dopants. In this study, we reveal a systematic transition from edge-state to bulk-state dominant supercurrents as the chemical potential varies from the bulk gap to the conduction band. This results in an evolution from a 2Φ0-periodic oscillation pattern to an asymmetric Fraunhofer pattern. Furthermore, a Fraunhoher-like pattern emerges due to the coexistence of chiral edge states and bulk states caused by magnetic domains, even when the chemical potential resides within the gap. These findings not only advance the theoretical understanding but also pave the way for the experimental discovery of the chiral Josephson effect based on QAHI doped with magnetic impurities. Published by the American Physical Society 2024

Ultralow lattice thermal conductivity in type-I Dirac MBene TiB2

MBenes, the emergent novel two-dimensional family of transition metal borides have recently attracted remarkable attention. Transport studies of such two-dimensional structures are very rare and are of sparking interest. In this paper Using Boltzmann transport theory with ab-initio inputs from density functional theory, we examined the transport in TiB2 MBene system, which is highly dependent on number of layers. We have shown that the addition of an extra layer (as in bilayer BL) destroys the formation of type-I Dirac state by introducing the positional change and tilt to the Dirac cones, thereby imparting the type-II Weyl metallic character in contrast to Dirac-semimetallic character in monolayer ML. Such non-trivial electronic ordering significantly impacts the transport behavior. We further show that the anisotropic room temperature lattice thermal conductivity κ L for ML (BL) is observed to be 0.41 (0.52) and 2.00 (2.04) W m−1 K−1 for x and y directions, respectively, while the high temperature κ L (ML 0.13 W m−1 K−1 and BL 0.21 W m−1 K−1 at 900 K in x direction) achieves ultralow values. Our analysis reveals that such values are attributed to enhanced anharmonic phonon scattering, enhanced weighted phase space and co-existence of electronic and phononic Dirac states. We have further calculated the electronic transport coefficients for TiB2 MBene, where the layer dependent competing behavior is observed at lower temperatures. Our results further unravels the layer dependent thermoelectric performance, where ML is shown to have promising room-temperature thermoelectric figure of merit (ZT) as 1.71 compared to 0.38 for BL.

Coexistence of antiferromagnetism and glassy magnetic state and signature of quantum interference effects in the frustrated ternary silicides HoScSi and ErScSi

Coexistence of antiferromagnetism and glassy magnetic state and signature of quantum interference effects in the frustrated ternary silicides HoScSi and ErScSi

Coexistence of state, choice, and sensory integration coding in barrel cortex LII/III

During perceptually guided decisions, correlates of choice are found as upstream as in the primary sensory areas. However, how well these choice signals align with early sensory representations, a prerequisite for their interpretation as feedforward substrates of perception, remains an open question. We designed a two alternative forced choice task (2AFC) in which male mice compared stimulation frequencies applied to two adjacent vibrissae. The optogenetic silencing of individual columns in the primary somatosensory cortex (wS1) resulted in predicted shifts of psychometric functions, demonstrating that perception depends on focal, early sensory representations. Functional imaging of layer II/III single neurons revealed mixed coding of stimuli, choices and engagement in the task. Neurons with multi-whisker suppression display improved sensory discrimination and had their activity increased during engagement in the task, enhancing selectively representation of the signals relevant to solving the task. From trial to trial, representation of stimuli and choice varied substantially, but mostly orthogonally to each other, suggesting that perceptual variability does not originate from wS1 fluctuations but rather from downstream areas. Together, our results highlight the role of primary sensory areas in forming a reliable sensory substrate that could be used for flexible downstream decision processes.

Unraveling the Harmonious Coexistence of Ruthenium States on a Self‐Standing Electrode for Enhanced Hydrogen Evolution Reaction

The development of cost‐effective, highly efficient, and durable electrocatalysts has been a paramount pursuit for advancing the hydrogen evolution reaction (HER). Herein, a simplified synthesis protocol was designed to achieve a self‐standing electrode, composed of activated carbon paper embedded with Ru single‐atom catalysts and Ru nanoclusters (ACP/RuSAC+C) via acid activation, immersion, and high‐temperature pyrolysis. Ab initio molecular dynamics (AIMD) calculations are employed to gain a more profound understanding of the impact of acid activation on carbon paper. Furthermore, the coexistence states of the Ru atoms are confirmed via aberration‐corrected scanning transmission electron microscopy (AC‐STEM), X‐ray photoelectron spectroscopy (XPS), and X‐ray absorption spectroscopy (XAS). Experimental measurements and theoretical calculations reveal that introducing a Ru single‐atom site adjacent to the Ru nanoclusters induces a synergistic effect, tuning the electronic structure and thereby significantly enhancing their catalytic performance. Notably, the ACP/RuSAC+C exhibits a remarkable turnover frequency (TOF) of 18 s−1 and an exceptional mass activity (MA) of 2.2 A mg−1, surpassing the performance of conventional Pt electrodes. The self‐standing electrode, featuring harmoniously coexisting Ru states, stands out as a prospective choice for advancing HER catalysts, enhancing energy efficiency, productivity, and selectivity.

Further study on the Rulkov neuron: geometric control, circuit realization and chaos-based encryption

Rulkov neuron with various firing modes is exhaustively explored by numerical simulation aiming to disclose its unique properties of evolution. Transient chaos and the coexistence of periodic state and chaos are found. Furthermore, it is found that the chaotic attractors in the neuron can also be arranged flexibly in phase space by a single offset booster, while the amplitude of firings is rescaled by an independent amplitude controller. Circuit implementation based on MCU is carried out demonstrating the predicted dynamics. Confidentiality and security of data play an important role in safeguarding national production and livelihood. In this paper, the chaotic firing is introduced into the Tiny Encryption Algorithm (TEA) for image encryption based on MCU combined with metrics analysis. It is proven that the Chaos-based Tiny Encryption Algorithm (ChaosTEA) exhibits higher efficiency and security compared to the traditional TEA algorithm.

In-situ crystallization of CoCr2O4 in tellurite glass with enhanced optical nonlinear limiting, photoluminescence, and magnetic properties: Influence of Co content

This article reports the in-situ growth of spinel CoCr2O4 nanocrystals (NC) in tellurite glass through tailoring the Co content by melt-quenching method. The microstructure, optical, and magnetic properties of NC/ glass systems were systematically studied using various techniques. Well-defined 30 nm crystallization of CoCr2O4 (space group of Fd3m) homogeneously distributed in the glassy matrix and the concurrent formation of cubic BiCoO3 (space group of P4mm) when the Co content exceeds 3%. The coexistence of multivalence and coordination states of Co and Cr significantly modified the glass structure with conversion of TeO4→TeO3, BO4→BO3, and CoO4→CoO6 units. Exceptional performance of the glass containing 5% Co-tuned CoCr2O4 was obtained, showcasing the decrease of Eg (2.09 eV), strong ferro-magnetization of 7.04 emu/g, large α3 (4.88×10−10 m/W) and good optical limiting property (threshhold of 1.31×1012 W/m2). Furthermore, the same glass showed excellent red emission between 650 and 800 nm under the excitation of 460 nm, with an increased lifetime (2.648 ms) and good stability of 90.7% within 25–300 °C. The emission mechanism was discussed. EPR analysis confirmed the active role and spin-states of magnetic Cr and Co ions, contributing synergistically to the improved optical and magnetic properties of the glasses.

Coexistence of varied intensities, phases, and polarization states along the direction of beam propagation

Polarization state, as one of the fundamental properties of light fields, has found widespread applications across various domains. The control of intensity, phase, and polarization state along the direction of beam propagation has opened up new avenues for beams. In this work, we generated a beam in which different intensities, phases, and polarization states can simultaneously appear at different positions along the direction of beam propagation. In other words, varied intensities, phases, and polarization states can coexist in the direction of beam propagation. The correctness of this method is validated through theoretical analysis and experimental results. This approach expands the application scope of light beams and provides a favorable path for exploring the optical characteristics of beams.

Coexistence of topological semimetal states in holography

We introduce a holographic model that exhibits a coexistence state of the Weyl semimetal and the topological nodal line state, providing us with a valuable tool to investigate the system’s behavior in the strong coupling regime. Nine types of bulk solutions exhibiting different IR behaviors have been identified, corresponding to nine different types of boundary states. These nine states include four distinct phases, namely the Weyl-nodal phase, the gap-nodal phase, the Weyl gap phase and the gap-gap phase, four phase boundaries, which are the Weyl-Dirac phase, the gap-Dirac phase, the Dirac-gap phase and the Dirac-nodal phase, and finally a double critical point. A phase diagram is plotted that exhibits qualitative similarity to the one obtained in the weak coupling limit. The anomalous Hall conductivity, which serves as an order parameter, and the free energy are calculated, with the latter showing the continuity of the topological phase transitions within the system. Our study highlights the similarities and differences in such a topological system between the weak and strong coupling regimes, paving the way for further experimental observations.

First-principles study on the coexistence of different valence states of Zn vacancy, Cu1+/2+ doping, and Hi in ZnO magnetic switch

In this study, we used first principles to investigate the magnetic sources and switches of Zn34Cu1+HiO36(VZn0), Zn34Cu1+HiO36(VZn2−), Zn34Cu2+HiO36(VZn0), and Zn34Cu2+HiO36(VZn2−) systems. On the basis of formation energy, phonon spectrum, and temporal variation of energy, we concluded that the above systems were all in a stable state. The doped system can be magnetized by adjusting the valence state of Zn vacancy, and the Zn34Cu1+HiO36(VZn0) and Zn34Cu2+HiO36(VZn2−) systems demonstrated magnetism. We found that the Zn34Cu1+HiO36(VZn0) system acquired magnetism through (O.↓↑+VZn")x⇔(↑O.+VZn"+↑O.)x⇔(↑O.+VZn"+↓O.)x super- and double-exchange interactions, whereas the magnetism of the Zn34Cu2+HiO36(VZn2−) system originated mainly from the action of the O1−–VZn2−–Cu2+-bound magnetic polaron and double exchange. Our theory provides a new approach for the use of magnetic switches in magnetic semiconductors.

Emergence of phase clusters and coexisting states reveals the structure-function relationship.

The Brain Connectome Project has made significant strides in uncovering the structural connections within the brain on various levels. This has led to the question of how brain structure and function are related. Our research explores this relationship in an adaptive neural network in which synaptic conductance between neurons follows spike-time synaptic plasticity rules. By adjusting the plasticity boundary, the network exhibits diverse collective behaviors, including phase synchronization, phase locking, hierarchical synchronization (phase clusters), and coexisting states. Using graph theory, we found that hierarchical synchronization is related to the community structure, while coexisting states are related to the hierarchical self-organizing and core-periphery structure. The network evolves into several tightly connected modules, with sparsely intermodule connections resulting in the formation of phase clusters. In addition, the hierarchical self-organizing structure facilitates the emergence of coexisting states. The coexistence state promotes the evolution of the core-periphery structure. Our results point towards the equivalence between function and structure, with function emerging from structure, and structure being influenced by function in a complex dynamic process.

Exploring the low-temperature polarization and the multifield-manipulated dielectric tunability behavior of NiMn2O4

Manganese oxides with spinel structure could exhibit abundant physical effects due to the complex sublattice structure, variable valence states and the intricate roles of manganese cations in magnetic interaction. In this work, NiMn2O4 ceramic with space group of Fd3‾m is synthesized. The low-temperature polarization behavior is investigated accompanied by revealing the multi-stage dielectric relaxation. Moreover, the relaxation mechanism is confirmed through microstructure characterization, multiple-condition pyroelectric measurement and the dielectric tunability properties under electric/magnetic fields. With increasing measuring temperature, different relaxation phenomena are respectively induced by lattice distortion because of the competition among magnetic coupling interactions (below ∼135 K), electron hopping relating to the coexistence of different valence states of manganese ions (∼135–230 K), and the synergistic contribution of oxygen vacancies and domain wall effect (above ∼230 K). These results provide additional evidence for comprehensive understanding the low-temperature polarization in NiMn2O4, guiding the method design for exploring the physical origin within a wide temperature range.

Strontium doping-tailored inverse spinel phase in cobalt chromite with enhanced photo-degradation of ofloxacin

Spinel materials are attractive to photocatalytic degradation of contaminants. In this study, strontium (Sr) doped spinel cobalt chromite (CoCr2O4) was synthesized by solution combustion method and characterized using techniques such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and electrochemical impedance spectroscopy (EIS). 30 -50 nm-cubic CoCr2O4 nanocrystals were obtained, and phase transitions of CoO6→CoO4 and CrO4→CrO6 occurred as the Sr doping content increased until 0.6 % Sr doped sample displayed an inverse spinel phase. The modifications in composition and structure induced the co-existence of multivalent states for Co and Cr, which in turn changed the optical, complex impedance, and magnetic spin state of CoCr2O4. The 0.6 % Sr-doped sample showed the highest photocatalytic efficiency of 93 % due to enhanced optical absorption, reduced energy band gap, oxygen vacancies formation, and a high spin state of Co. The XRD structure and photocatalytic activity remained stable even after five cycles without any leakage of metal elements. The degradation pathway and Mott-Schottky curves were employed to elucidate the mechanism behind this enhancement. The strategy employed in this study proved effective, and the synthesized materials show promise for the photocatalytic degradation of contaminants.

Multiple magnetic transition and magnetocaloric properties in the mixed valence Eu8CuNi2.5Si42.5 type I clathrate compound

We investigated the magnetocaloric and electrical transport properties of the Eu8CuNi2.5Si42.5 clathrate compound, synthesized by an arc melting and annealing method. X-ray photoemission spectroscopy revealed a mixed valence state of Eu2+ and Eu3+. The low-field and low-temperature magnetic measurements indicated a multiple magnetic transition, from ferromagnetic near 35 K to antiferromagnetic at 25 K. Increasing the magnetic field led to the broadening of antiferromagnetic peaks and a final ferromagnetic state under high magnetic fields, indicative of spin reorientation. The transition from a ferromagnetic to an antiferromagnetic state was further corroborated by specific heat measurements. We noted spontaneous magnetization at low temperatures via magnetic hysteresis and Arrott plot analysis. The coexistence of an antiferromagnetic ground state (attributed to the Eu2+ ions) and ferromagnetic clusters (associated with the Ni2+ ions) was supported by spontaneous magnetization at low temperatures in the antiferromagnetic state. The magnetocaloric analyses revealed a high spin entropy change over a broad temperature range for Eu8CuNi2.5Si42.5, which implies its potential as a robust low-temperature magnetocaloric material, distinguished by its high refrigerant capacity.

SUPPORTING INSTRUMENTS OF THE EUROPEAN UNION FOR RESOLVING CONFLICTS WITHIN THE UNION

The European Union, a community consisting of 27 member states with completely different histories, cultures, economies and levels of development, needs certain clear rules of the game that will ensure peaceful coexistence and continuity of coexistence of states gathered under one integration roof. This article focuses on the principle of subsidiarity in the EU and its role in conflict management. The purpose of this article is to provide a comprehensive overview of how subsidiarity operates as a mechanism to reduce tensions and promote cooperation between EU member states. The analysis focuses on the historical application of this principle in different political contexts to identify patterns and general trends. The methodological approach of the article is based on a comprehensive analysis of political decision-making processes at the EU level, taking into account the principle of subsidiarity. By combining qualitative and quantitative research methods, the impact of this principle on conflict identification, prevention and resolution is systematically explored. It was confirmed that targeted and effective implementation of the principle of subsidiarity in the EU can make a significant contribution to conflict prevention and resolution. Principle of subsidiarity acts as the main tool for conflict management in the EU, plays a central role.

Bonding properties and superconductivity of electride Be6C under moderate pressure

Superconducting electrides are characterized by the emergence of electrons occupying the interstitial region of lattice and exhibit coexistence of distinctive electride state and superconductivity, which have attracted wide attention. However, the underlying crucial factors governing the superconductivity and influencing the structural stability by electride states remain elusive. Here, we performed structure searches in conjunction with first-principles calculations to identify a dynamically stable electride Be6C at 40 GPa, which exhibits p-orbital type electride states and demonstrates superconductivity with a Tc of 22.4 K. Furthermore, it remains dynamically stable even down to ambient conditions while maintaining a Tc of 18.9 K. Further analyses unveiled that the dual p-hybridized electrons within the orbitals of p-orbital electride states and Be-2p mainly composed of a van Hove singularity near the Fermi level and participate in electron–phonon interaction to form Cooper pairs leading to the high-Tc. The preservation of dynamic stability for Be6C at low pressure is primarily attributed to the presence of electride states that effectively form both covalent and ionic bonding properties to bind neighbor Be cations to lower enthalpy of system and subsequently, in turn, lowering the required pressure. Our findings not only explained the underlying factors affecting superconductivity but also revealed the crucial role of electride states in determining the dynamic stability of structure, providing valuable insights for subsequent research on superconducting electrides at low pressures.

Molecular Motors' Magic Methyl and Its Pivotal Influence on Rotation.

Molecular motors have found a wide range of applications, powering a transition from molecules to dynamic molecular systems for which their motion must be precisely tuned. To achieve this adjustment, strategies involving laborious changes in their design are often used. Herein, we show that control over a single methyl group allows a drastic change in rotational properties. In this regard, we present the straightforward asymmetric synthesis of β-methylated first-generation overcrowded-alkene-based molecular motors. Both enantiomers of the new motors were prepared in good yields and high enantiopurities, and these motors were thoroughly studied by variable-temperature nuclear magnetic resonance (VT-NMR), ultraviolet-visible (UV-vis), and circular dichroism (CD) spectroscopy, showing a crucial influence of the methylation pattern on the rotational behavior of the motors. Starting from a common chiral precursor, we demonstrate that subsequent methylation can drastically reduce the speed of the motor and reverse the direction of the rotation. We show for the first time that complete unidirectionality can be achieved even when the energy difference between the stable and metastable states is small, resulting in the coexistence of both states under ambient conditions without hampering the energy ratcheting process. This discovery opens the way for the design of more advanced first-generation motors.