Moderate Coupling Research Articles

Research on modeling method for connectors in the train-track-bridge system based on multi-timestep explicit-implicit co-simulation

For the response of the train-track-bridge system under extreme environment, an increasing number of studies employ co-simulation strategies for detailed modeling and calculation of the structure. However, there is a lack of research on the module connectors, which significantly impact simulation accuracy and stability. In this paper, the theoretical differences between weak, moderate, and strong coupling methods in dealing with co-simulation module interface connectors are discussed. An explicit-implicit multi-timestep co-simulation platform is established using MATLAB and OPENSEES software. Taking China's CRTS II slab ballastless track, a simply supported beam bridge, and a train as examples, a three-dimensional train-track-bridge coupling model is created. The three coupling methods are then verified and compared. Finally, two coupling methods are used to model and calculate the train-track-bridge system under earthquake. It is concluded that when calculating the train-track-bridge under earthquake, using the fastener with less damage as the co-simulation partition boundary can avoid complex nonlinear calculation. On this basis, it is feasible to use weak, moderate and strong coupling methods to deal with fastener elements. Different co-simulation software can adopt different coupling methods according to the difficulty of modeling. In the MATLAB-OPENSEES multi-timestep explicit-implicit co-simulation platform, the weak and moderate methods can achieve better calculation accuracy, and can be used to calculate the response of train-track-bridge system under earthquake.

Q-balls in the presence of attractive force

Q-balls are non-topological solitons in field theories whose stability is typically guaranteed by the existence of a global conserved charge. A classic realization is the Friedberg-Lee-Sirlin (FLS) Q-ball in a two-scalar system where a real scalar χ triggers symmetry breaking and confines a complex scalar Φ with a global U(1) symmetry. A quartic interaction κχ2|Φ|2 with κ > 0 is usually considered to produce a nontrivial Q-ball configuration, and this repulsive force contributes to its stability. On the other hand, the attractive cubic interaction Λχ|Φ|2 is generally allowed in a renormalizable theory and could induce an instability. In this paper, we study the behavior of the Q-ball under the influence of this attractive force which has been overlooked. We find approximate Q-ball solutions in the limit of weak and moderate force couplings using the thin-wall and thick-wall approximations respectively. Our analytical results are consistent with numerical simulations and predict the parameter dependencies of the maximum charge. A crucial difference with the ordinary FLS Q-ball is the existence of the maximum charge beyond which the Q-ball solution is classically unstable. Such a limitation of the charge fundamentally affects Q-ball formation in the early Universe and could plausibly lead to the formation of primordial black holes.

Bridge vs Terminal Cyano-coordination in Binuclear Cobalt Porphyrin Dimers: Interplay of Electrons between Metal and Ligand and Spin-Coupling via Bridge.

Three cyano-coordinated cobalt porphyrin dimers were synthesized and thoroughly characterized. The X-ray structure of the complexes reveals that cyanide binds in a terminal fashion in both the anti and trans isomers of ethane- and ethylene-bridged cobalt porphyrin dimers, while in the cis ethylene-bridged dimer, cyanides bind in both terminal and bridging modes. The nonconjugated ethane-bridged complex stabilizes exclusively a diamagnetic metal-centered oxidation of type CoIII(por)(CN)2 both in the solid and in solution. In contrast, the complexes with the conjugated ethylene-bridge contain signatures of both paramagnetic ligand-centered oxidation of the type CoII(por•+)(CN)2 and diamagnetic metal-centered oxidation of type CoIII(por)(CN)2 with the metal-centered oxidized species being the major component in the solid state as observed in XPS, while the ligand-centered oxidized species are present in a significant amount in solution. 1H NMR spectrum in solution displays two set of signals corresponding to the simultaneous presence of both the diamagnetic and paramagnetic species. EPR and magnetic investigation reveal that there is a moderate ferromagnetic coupling between the unpaired electrons of the low-spin CoII center and the porphyrin π-cation radical in CoII(por•+)(CN)2 species as well as an antiferromagnetic coupling between the two CoII(por•+) units through the ethylene and CN bridges.

Synergy of Oxygen Octahedra Distortion and Polar Nanodomains Induced Emergent Electrocaloric Effect in NaNbO3-Based Ceramics.

High-performance electrocaloric materials are essential for the development of solid-state cooling technologies; however, the contradiction of the electrocaloric effect (ECE) and temperature span in ferroelectrics frustrates practical applications. In this work, through modulating oxygen octahedra distortion and short-range polar nanodomains with moderate coupling strength, an EC value of ΔT ∼ 0.30 K with an ultrawide temperature span of 85 K is obtained in the x = 0.04 composition [(0.88 - x)NaNbO3-0.12BaTiO3-xLiSbO3 (x = 0-0.06)]. The LiSbO3 dopant induces a P4bm-to-R3cH phase transition and intensifies the oxygen octahedra distortion degree, accompanied by the ferroelectric domain smashing into polar nanodomains. Also, LiSbO3 addition enhances the relaxation degree with a downshift of Tfd (ferroelectric-to-diffuse phase transition temperature) and TJ (temperature of the maximal current density value), and Tfd is shifted to near room temperature with an absence of TJ in x = 0.04. Local energy barriers induced by oxygen octahedra distortion inhibit the phase transition in conjunction with activation of short-range polar order switching under thermal stimuli, which is the underlying mechanism for an excellent EC performance for x = 0.04. This work not only clarifies that ferroelectrics with oxygen octahedra distortion and short-range polar order are expected to achieve remarkable EC performances but also provides a design strategy to seek emergent EC behaviors in complex oxygen-octahedra-distortion materials.

Exciton Transport in the Nonfullerene Acceptor O-IDTBR from Nonadiabatic Molecular Dynamics.

Theory, computation, and experiment have given strong evidence that charge carriers in organic molecular crystals form partially delocalized quantum objects that diffuse very efficiently via a mechanism termed transient delocalization. It is currently unclear how prevalent this mechanism is for exciton transport. Here we carry out simulation of singlet Frenkel excitons (FE) in a molecular organic semiconductor that belongs to the class of nonfullerene acceptors, O-IDTBR, using the recently introduced FE surface hopping nonadiabatic molecular dynamics method. We find that FE are, on average, localized on a single molecule in the crystal due to sizable reorganization energy and moderate excitonic couplings. Yet, our simulations suggest that the diffusion mechanism is more complex than simple local hopping; in addition to hopping, we observe frequent transient delocalization events where the exciton wave function expands over 10 or more molecules for a short period of time in response to thermal excitations within the excitonic band, followed by de-excitation and contraction onto a single molecule. The transient delocalization events lead to an increase in the diffusion constant by a factor of 3-4, depending on the crystallographic direction as compared to the situation where only local hopping events are considered. Intriguingly, O-IDTBR appears to be a moderately anisotropic 3D "conductor" for excitons but a highly anisotropic 2D conductor for electrons. Taken together with previous simulation results, two trends seem to emerge for molecular organic crystals: excitons tend to be more localized and slower than charge carriers due to higher internal reorganization energy, while exciton transport tends to be more isotropic than charge transport due to the weaker distance dependence of excitonic versus electronic coupling.

Recovering Complete Positivity of Non-Markovian Quantum Dynamics with Choi-Proximity Regularization

A relevant problem in the theory of open quantum systems is the lack of complete positivity of dynamical maps obtained after weak-coupling approximations, a famous example being the Redfield master equation. A number of approaches exist to recover well-defined evolutions under additional Markovian assumptions, but much less is known beyond this regime. Here, we propose a numerical method to cure the complete-positivity violation issue while preserving the non-Markovian features of an arbitrary original dynamical map. The idea is to replace its unphysical Choi operator with its closest physical one, mimicking recent work on quantum process tomography. We also show that the regularized dynamics is more accurate in terms of reproducing the exact dynamics, which allows us to heuristically push the utilization of these master equations in moderate coupling regimes, where the loss of positivity can have a relevant impact. Published by the American Physical Society 2024

A coupled model between circadian, cell-cycle, and redox rhythms reveals their regulation of oxidative stress

Most organisms possess three biological oscillators, circadian clock, cell cycle, and redox rhythm, which are autonomous but interact each other. However, whether their interactions and autonomy are beneficial for organisms remains unclear. Here, we modeled a coupled oscillator system where each oscillator affected the phase of the other oscillators. We found that multiple types of coupling prevent a high H2O2 level in cells at M phase. Consequently, we hypothesized a high H2O2 sensitivity at the M phase and found that moderate coupling reduced cell damage due to oxidative stress by generating appropriate phase relationships between three rhythms, whereas strong coupling resulted in an elevated cell damage by increasing the average H2O2 level and disrupted the cell cycle. Furthermore, the multicellularity model revealed that phase variations among cells confer flexibility in synchronization with environments at the expense of adaptability to the optimal environment. Thus, both autonomy and synchrony among the oscillators are important for coordinating their phase relationships to minimize oxidative stress, and couplings balance them depending on environments.

Statistical modeling of 3D seismicity and its correlation with fault slips along major faults in California

This study applies a 3D Epidemic Type Aftershock Sequence (ETAS) model to the earthquake catalog in California. A new depth kernel function incorporating the scaling effect of mainshock magnitudes is introduced into the model. The results demonstrate that the new model improves data fitting, and we find a consistent decrease in aftershock productivity with depth by stochastic reconstruction. We attribute this to the decreasing fault coupling with depth or active seismic faulting in the upper crust. Furthermore, we compare background seismicity rates derived from the new model with the long-term slip rates on the faults in the study region. We reveal a linear increase in the seismicity rate with the slip rate on the logarithmic scale, suggesting the accumulated strain on fault is partially released by seismic activities. Additionally, a significant correlation exists between the background seismicity rate and fault segments exhibiting relatively high creep rates, especially in the transition zones for fault coupling along the central San Andreas fault. This finding suggests that interseismic background earthquakes mostly occur in areas with moderate coupling ratios.

Temporal and Spatial Analysis of Coupling Coordination in Beijing–Tianjin–Hebei Urban Agglomeration: Ecology, Environment and Economy

With the rapid growth and development of urban areas, the economy has often been prioritized at the expense of the environment and ecological systems. However, it is essential to delve deeper into the relationship between the economy and the ecological environment. Therefore, this study introduces a comprehensive evaluation system that encompasses economic, ecological, and environmental factors in the Beijing–Tianjin–Hebei urban agglomeration in China. The Criteria Importance Through Inter-criteria Correlation (CRITIC) method is utilized to determine the weights of various indicators, and coupling as well as coupling coordination models are employed to investigate the spatiotemporal trends and interrelationships of the three factors. The results indicate that the economic development index has displayed a consistent uptrend since 2000, with the economic development index from 2015–2020 increasing by approximately four times compared to 2000–2005. The ecological status index has also increased in the last five years, with a rise of about 0.05 from 2015–2020 compared to 2000–2005. The environmental status index has fluctuated but generally increased, with a rise of approximately 5.6 times from 2015–2020 compared to 2000–2005. The coupling degree of the Beijing–Tianjin–Hebei urban agglomeration is relatively high, with intense coupling from 2005–2020, and moderate coupling from 2000–2005. Furthermore, the coupling coordination has continuously improved from mild maladjustment to barely coordinated from 2000 to 2020, indicating the enhancement of the coupling coordination of the three factors. It is crucial to acknowledge that there exists spatial heterogeneity in both the coupling degree and coupling coordination degree. This heterogeneity stems from the uneven progress in economic development, ecological conditions, and environmental status across various cities. Additional endeavors are required to foster the harmonized advancement of these factors across the entire region.

Light squeezing enhancement by coupling nonlinear optical cavities

In this paper, we explore the squeezing effect generated by two coupled optical cavities. Each cavity contains a second-order nonlinear material and coherently pumped by a laser. Our results show that light intensity is strongly improved due to the presence of the nonlinearities and mainly depends on the detunings between external laser frequencies and cavity modes. More interestingly, the proposed scheme could enhance light squeezing for moderate coupling between cavities : the squeezing generated by one cavity is enhanced by the other one. For resonant interaction, highest squeezing effect is obtained near resonance. When fields are non resonant, squeezing increases near resonance of the considered cavity, but decreases for large detunings relative to the second cavity. Further, when the dissipation rate of the second cavity is smaller than the first, the squeezing could be improved, attaining nearly the perfect squeezing. While the temperature elevation has a negative impact overall on the nonclassical light, squeezing shows an appreciable resistance against thermal baths for appropriate parameter sets.

Variational principles for the hydrodynamics of the classical one-component plasma

Hydrodynamic equations for a one-component plasma are derived as a unification of the Euler equations with long-range Coulomb interaction. By using a variational principle, these equations self-consistently unify thermodynamics, dispersion laws, nonlinear motion, and conservation laws. In the moderate and strong coupling limits, it is argued that these equations work down to the length scale of the interparticle spacing. The use of a variational principle also ensures that closure is achieved self-consistently. Hydrodynamic equations are evaluated in both the Eulerian frame, where the fluid variables depend on the position in the laboratory, and the Lagrangian frame, where they depend on the position in some reference state, such as the initial position. Each frame has its advantages and our final theory combines elements of both. The properties of longitudinal and transverse dispersion laws are calculated for the hydrodynamic equations. A simple step function approximation for the pair distribution function enables simple calculations that reveal the structure of the equations of motion. The obtained dispersion laws are compared to molecular dynamics simulations and the theory of quasilocalized charge approximation. The action, which gives excellent agreement for both longitudinal and transverse dispersion laws for a wide range of coupling strengths, is elucidated. Agreement with numerical experiments shows that such a hydrodynamic approach can be used to accurately describe a one-component plasma at very small length scales comparable to the average interparticle spacing. The validity of this approach suggests considering nonlinear flows and other systems with long-range interactions in the future.

Azo-Cyanamide Bridged Dinuclear Iron Complexes Exhibiting no Electronic Coupling but Moderate Magnetic Coupling between the two Iron Centers.

To investigate the effect of long-distance organic ligand on electronic coupling between metallic atoms, the mononuclear and dinuclear complexes [Cp(dppe)Fe(apc)] (1), [{Cp(dppe)Fe}2(μ-adpc)] (2), [{CpMe5(dppe)Fe}2(μ-adpc) (3) and their oxidized complexes [Cp(dppe)Fe(apc)][PF6] (1[PF6]), [{Cp(dppe)Fe}2(μ-adpc)][PF6] (2[PF6]2), [{CpMe5(dppe)Fe}2(μ-adpc)][PF6]2 (3[PF6]2) (Cp=1,3-cyclopentadiene, CpMe5=1,2,3,4,5-pentamethylcyclopentadiene, dppe=1,2-bis(diphenylphosphino)ethane), apc-=4-azo(phenylcyanamido)benzene and adpc2-=4,4'-azodi(phenylcyanamido)) were synthesized and characterized by cyclic voltammetry, UV-vis, single-crystal X-ray diffraction and Mössbauer spectra. Electrochemical measurements showed no electronic coupling between the two terminal Fe units, However, the investigation results of the magnetic properties of the two-electron oxidized complexes indicate the presence of moderate antiferromagnetic coupling across 18 Å distance.

Digital quantum simulation of non-perturbative dynamics of open systems with orthogonal polynomials

Classical non-perturbative simulations of open quantum systems' dynamics face several scalability problems, namely, exponential scaling of the computational effort as a function of either the time length of the simulation or the size of the open system. In this work, we propose the use of the Time Evolving Density operator with Orthogonal Polynomials Algorithm (TEDOPA) on a quantum computer, which we term as Quantum TEDOPA (Q-TEDOPA), to simulate non-perturbative dynamics of open quantum systems linearly coupled to a bosonic environment (continuous phonon bath). By performing a change of basis of the Hamiltonian, the TEDOPA yields a chain of harmonic oscillators with only local nearest-neighbour interactions, making this algorithm suitable for implementation on quantum devices with limited qubit connectivity such as superconducting quantum processors. We analyse in detail the implementation of the TEDOPA on a quantum device and show that exponential scalings of computational resources can potentially be avoided for time-evolution simulations of the systems considered in this work. We applied the proposed method to the simulation of the exciton transport between two light-harvesting molecules in the regime of moderate coupling strength to a non-Markovian harmonic oscillator environment on an IBMQ device. Applications of the Q-TEDOPA span problems which can not be solved by perturbation techniques belonging to different areas, such as the dynamics of quantum biological systems and strongly correlated condensed matter systems.

Theoretical elucidation of the effect of the linkage and orientation of carbazole and naphthalenediimide on the TADF and RTP propensities.

Thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) are most promising processes for harvesting triplet excitons in organic light-emitting diodes. In this work, the effect of the linkage between the carbazole (Cz) donor (D) and the naphthalenediimide (NDI) acceptor (A) on the TADF and RTP propensities is elucidated using density functional theory computations employing D-A, D-A-D, D-π-A, and D-π-A-π-D structural designs. The effects of the dihedral angle between the donor and acceptor units on the energy difference between the singlet and triplet excited states (ΔEST), the spin-orbit coupling (SOC) constants, and radiative (kr), intersystem crossing (kISC) and reverse intersystem crossing (kRISC) rates are unravelled. The molecules possessing a direct linkage between Cz and NDI exhibit large ΔEST values due to substantial overlap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). However, the insertion of a phenyl spacer between the Cz and NDI units led to disjoint HOMO and LUMO and consequently resulted in a small ΔEST. Furthermore, the presence of two donors with and without a phenyl spacer on NDI resulted in a high-lying triplet state (T2) that is energetically lower than the lowest singlet excited state (S1), hence providing additional channels to the TADF and RTP processes. Also, the orientation of Cz and NDI in the ortho-positions of the phenyl unit resulted in a T1 state with dominant LE character which led to moderate spin-orbit coupling constants and highest kr rates compared to the analogous meta- and para-linked derivatives. Thus, the ortho-derivatives possessed small ΔEST, charge transfer dominated S1, joint holes and electrons for the T1 state, characteristic of local excitation, high SOC, and promising rISC and kr rates. Overall, the phenyl linked derivatives possess TADF characteristics, while the directly linked analogues show RTP propensity.

Biaxial strain modulated electronic structures of layered two-dimensional MoSiGeN4 Rashba systems.

The two-dimensional (2D) MA2Z4 family has received extensive attention in manipulating its electronic structure and achieving intriguing physical properties. However, engineering the electronic properties remains a challenge. Herein, based on first-principles calculations, we systematically investigate the effect of biaxial strains on the electronic structure of 2D Rashba MoSiGeN4 (MSGN), and further explore how the interlayer interactions affect the Rashba spin splitting (RSS) in such strained layered MSGN systems. After applying biaxial strains, the band gap decreases monotonically with increasing tensile strains but increases when the compressive strains are applied. An indirect-direct-indirect band gap transition is induced by applying a moderate compressive strain (<5%) in the MSGN systems. Due to the symmetry breaking and moderate spin-orbit coupling (SOC), the monolayer MSGN possesses an isolated RSS near the Fermi level, which could be effectively regulated to the Lifshitz-type spin splitting (LSS) by biaxial strain. For instance, the LSS ← RSS → LSS transformation of the Fermi surface is presented in the monolayer and a more complex and changeable LSS ← RSS → LSS → RSS evolution is observed in bilayer and trilayer MSGN systems as the biaxial strain varies from -8% to 12%, which actually depends on the appearance, variation, and vanish of the Mexican hat band in the absence of SOC under different strains. The contribution of the Mo-dz2 orbital hybridized with the N-pz orbital in the highest valence band plays a dominant role in band evolution under biaxial strains, where the RSS → LSS evolution corresponds to the decreased Mo-dz2 orbital contribution. Our study highlights the biaxial strain controllable RSS, in particular the introduction and even the evolution of LSS near the Fermi surface, which makes the strained MSGN systems promising candidates for future applications in spintronic devices.

Exploring superconductivity in Ba3Ir4Ge16: Experimental and theoretical insights

We explore both experimental and theoretical aspects of the superconducting properties in the layered caged compound, Ba3Ir4Ge16. Our approach integrates muon spin rotation and relaxation (μSR) measurements with magnetization and heat capacity experiments, accompanied by first-principle calculations. The compound’s bulk superconductivity is unequivocally established through DC magnetization measurements, revealing a critical temperature (TC) of 5.7 K. A noteworthy characteristic observed in the low-temperature superfluid density is its saturating behavior, aligning with the features typical of conventional Bardeen-Cooper-Schrieffer (BCS) superconductors. The assessment of moderate electron-phonon coupling superconductivity is conducted through transverse field μSR measurements, yielding a superconducting gap to TC ratio (2Δ(0)∕kBTC) of 4.04, a value corroborated by heat capacity measurements. Crucially, zero field μSR measurements dismiss the possibility of any spontaneous magnetic field emergence below TC, highlighting the preservation of time-reversal symmetry. Our experimental results are reinforced by first-principles density functional calculations, underscoring the intricate interplay between crystal structure and superconducting order parameter symmetry in caged compounds. This comprehensive investigation enhances our understanding of the relationship between crystal structure and superconductivity in such unique compounds.

Nature of Overcharging and Charge Inversion in Electrical Double Layers.

Understanding overcharging and charge inversion is one of the long-standing challenges in soft matter and biophysics. To study these phenomena, we employ the modified Gaussian renormalized fluctuation theory, which allows for the self-consistent accounting of spatially varying ionic strength as well as the spatial variations in dielectric permittivity and excluded volume effects. The underlying dependence of overcharging on the electrostatic coupling is elucidated by varying the surface charge, counterion valency, and dielectric contrast. Consistent with simulations, three characteristic regimes corresponding to weak, moderate, and strong coupling are identified. Important features like the inversion of zeta potential, crowding, and ionic layering at the surface are successfully captured. For weak coupling, there is no overcharging. In the moderate coupling regime, overcharging increases with the surface charge. Finally, in the strong coupling regime, ionic crowding and saturation in overcharging are observed. Our theory predicts a nonmonotonic dependence of charge inversion on multivalent salt concentration as well as the addition of monovalent salt, in quantitative agreement with experiments.

INCREASED LEVELS OF PROINFLAMMATORY CYTOKINES IN BLOOD PLASMA IN PATIENTS WITH CHRONIC THROMBOEMBOLIC PULMONARY HYPERTENSION

HighlightsIL-8 and MCP-1 have a significant role in the CTEPH pathogenesis, which indicates the importance of nonspecific immunity in the formation and progression of CTEPH. The coupling between cytokines and hemodynamic parameters, cardiac structural changes and plasma biochemical parameters were determined. AbstractBackground. Chronic thromboembolic pulmonary hypertension (CTEPH) pathogenesis is complex and not fully understood. Particular attention to the microvascular damage genesis in CTEPH is given to aseptic inflammation, which in turn could be mediated through various molecular mechanisms. According to the conflicting and incomplete data on changes in the profile of factors controlling inflammation in CTEPH, research in this field would identify new therapeutic targets for the prevention and treatment of CTEPH.Aim. To study the profile of plasma proinflammatory cytokines in patients with chronic thromboembolic pulmonary hypertension (CTEPH) and evaluate the coupling of these cytokines with the main morphofunctional and laboratory values of the disease severity.Methods. 34 patients with CTEPH were included in this study. To characterize the group, the following methods were used: echocardiographic examination, catheterization of the right cardiac chambers. Biomarkers of heart failure, systemic inflammation, as well as erythropoiesis and iron metabolism were assessed in all patients. The control group included 10 donors. To study the proinflammatory cytokine profile in plasma, interleukins (IL) 6, 8, 18, monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase 9 were determined using standard enzyme-linked immunosorbent assay (ELISA) kits.Results. Hemodynamic and morphofunctional changes in the pulmonary circulation specific to pulmonary hypertension were determined with catheterization of the right cardiac chambers and echocardiography. During plasma proinflammatory cytokines analysis, a significant increase in the level of IL-8 (p = 0.030) and MCP-1 (p = 0.031) in CTEPH group compared to the control group was observed. No significant differences for other analyzed markers were found. In the elaboration of the correlation analysis, moderate inverse coupling between proinflammatory markers and hemodynamic parameters characterizing the CTEPH severity were revealed, as well as positive correlations with parameters of remodeling of the right cardiac chambers and iron metabolism.Conclusion. The increased levels of IL-8 and MCP-1 in patients with CTEPH identified in the present study indicate a significant role of nonspecific immunity in the formation and progression of CTEPH. The coupling between cytokines and hemodynamic parameters, structural cardiac changes and plasma biochemical parameters were determined. Based on the obtained data, it is possible to develop new medicinal substances, targeting towards proinflammatory cytokines, their receptors and signaling pathways.

Magnon-magnon entanglement generation between two remote interaction-free optomagnonic systems via optical Bell-state measurement

Finding new strategies for the generation and preservation of quantum resources, e.g. entanglement between spatially separated macroscopic systems enables reliable and fertile platforms to study both fundamental quantum physics and fruitful applications such as quantum networks and distant quantum information processing. Here, we want to address how to generate magnon-magnon entanglement (MME) in an optomagnonic system based on the optical Bell-state measurement. To do so, we consider a hybrid optomagnonic system comprising of two identical, but distant dissipative microwave cavities, each containing a ferromagnetic YIG sphere and a superconducting qubit. Besides, each subsystem is driven via an external laser field. We numerically simulate the solution of the corresponding master equation and discuss the time-dependent as well as the steady state entanglement between the distant magnon modes at different interaction regime. Also, the fidelity of the generated entangled states is studied in detail. Generally, the dissipative environmental effects plague the MME, however, it is possible to generate a considerable amount of MME even at the steady state regime. Also, the results show that the robust MME may be enhanced by applying a relatively strong external pump decreasing the relative magnon damping rate as well as increasing the relative qubit-photon coupling strength, while some other parameters involved in the model, i.e. the atomic damping rate and detuning parameter do not considerably affect the amplitude (the maximum value) of MME. Exceptionally, although the magnon damping rate decreases the amount of MME, the entanglement stability takes place in a longer time interval in the strong magnonic damping regime. Moreover, the maximum of the steady state entanglement may be obtained in the moderate magnon-photon coupling regime provided that the system is driven by strong external pumps. Furthermore, the system can generate robust MME at steady state, especially in the small detuning regime. Our further investigations show that the system can provide relatively high-fidelity magnonic entangled states even in the presence of inevitable environmental effects. The proposed model offers an attractive platform for the generation of quantum resources to establish long-distance quantum networks based on magnonic and photonic systems.

Giant four-fold magnetic anisotropy in nanotwinned NiMnGa epitaxial films

A giant four-fold magnetic anisotropy (with an anisotropy field up to 4 kOe) was observed in the twinned NiMnGa epitaxial film. Its appearance is explained in terms of moderate coupling between twin variants having strong uniaxial magnetocrystalline anisotropies directed orthogonally when the intertwin exchange field is comparable with the anisotropy field. This finding paves the way to increase the order of magnetic anisotropy in a many-component system while keeping the value of the anisotropy field by tuning the intercomponent exchange strength and can be extended to exchange-coupled multilayers and arrays of nanoelements.