arXiv subjects

Zhijun Jiang

Publications and source records attributed to Zhijun Jiang.

At least 19 recordsLinked to original sources

arXiv2026

Odd-Parity Chiral Magnons in Collinear Antiferromagnetic Multiferroics

Odd-parity magnetism represents an intriguing frontier in unconventional magnets; however, its realization has traditionally relied on noncollinear magnetic orders accompanied by broken spin conservation, which inevitably causes spin relaxation and dissipative transport of spin-encoded information. Here, we uncover a distinct route toward spin-conserving odd-parity magnon splitting enabled by antichiral Haldane-like flux (AHF) in collinear antiferromagnetic multiferroics. Symmetry analysis reveals that such AHF driven by intra-sublattice Dzyaloshinskii-Moriya interactions (DMI) gives rise to symmetry-dependent odd-parity magnon splittings, ranging from $p$-wave and $f$-wave to nodeless forms. Moreover, the coupling between ferroelectric modes and DMI provides an electric-field knob for manipulating chiral band splitting and magnon transport. Combining density functional theory (DFT) calculations, we identify a series of promising candidate materials in both 2D and bulk antiferromagnetic multiferroics. Our work provides new insights into the realization of odd-parity chiral magnons in collinear antiferromagnets and magnetoelectric coupling mechanisms in multiferroics.

cond-mat.mtrl-sci↗

arXiv2026

Light-Driven Ferroic Switching Enables Reversible Control of Hydrogen Adsorption Thermodynamics

Reversible ultrafast switching of surface thermodynamics is highly desirable for hydrogen storage and catalysis yet remains elusive at the nanoscale. Here we demonstrate that photoinduced ferroic-order switching in two-dimensional ionic ferroelectric monolayers enables rapid, reversible control of hydrogen binding. In TiGeSe$_3$, carrier-density-driven redistribution of transition-metal 3\textit{d} orbital occupations triggers a sequential evolution from the ferroelectric ground state to paraelectric phases with staggered or Zig-Zag antiferromagnetic order. This switch continuously tunes the hydrogen adsorption free energy from 0.33 to 1.11 eV, shifting the interface from near-thermoneutrality to spontaneous desorption. Nonadiabatic dynamics indicate that electron-phonon coupling promotes nonthermal H release, while picosecond carrier recombination rapidly restores the initial ferroic order, closing an ultrafast reversible cycle. Generality is further validated in AgBiP$_2$Se$_6$ and CuInP$_2$S$_6$, establishing ferroic order as an optically addressable knob for dynamic thermodynamic reconfiguration beyond static design.

cond-mat.mtrl-sci↗

arXiv2026

Electric-Switchable Chiral Magnons in PT-Symmetric Antiferromagnets

The magnons in antiferromagnetic insulators (AFIs) exhibit dual chirality, each carrying opposite spin angular momentum. However, in PT-symmetric AFIs, the magnon bands remain degenerate. In this work, we introduce a new class of PT-preserving AFIs in which the giant chiral splitting of magnons can be induced and controlled by an external electric field. Unlike conventional cases, such AFIs host a hidden dipole coupled to the antiferromagnetic order, which allows an external electric field to break the magnon sublattice symmetry and thereby largely lift the band degeneracy. Group theoretical analysis identifies the possible magnetic layer groups, while first-principles calculations and spin-wave theory reveal band splittings up to 20meV in Cr2CCl2 and Cr2CBr2 under the electric field of 0.2 V/Å, corresponding to an effective magnetic field of 200T. In addition, the electrically controlled magnon chiral splitting enables reversible switching of magnon-mediated spin currents. These findings open a new route toward nonvolatile spintronics based on magnons.

cond-mat.mtrl-sci↗

arXiv2026

SPARK: Secure Predictive Autoscaling for Robust Kubernetes

Achieving high availability and robust security in Kubernetes requires more than reactive scaling and standard perimeter firewalls. Traditional autoscalers, such as HPA, often fail to react quickly to traffic spikes and cannot distinguish between legitimate flash crowds and DDoS attacks. We present an open-source toolchain to provide a traffic-aware autoscaling approach that utilizes an eBPF-based networking layer to enforce security policies at the kernel level while orchestrating scaling decisions based on predictive models. Our results demonstrate that the predictive approach reduces timeout errors by 32% during sudden traffic surges compared to standard reactive scaling, while ensuring immediate network convergence and layer 7 security isolation for newly scaled pods.

cs.CR↗

arXiv2025

Ferroelectric Switchable Topological Magnon Hall Effect in Type-I Multiferroics

Electric control of magnetism at room temperature is crucial for developing next-generation, low-power spintronic devices. However, the intrinsic incompatibility between ferroelectricity and magnetism in crystal symmetry, along with the absence of strong magnetoelectric coupling mechanisms, continues to pose major challenges. In this work, we propose a general theoretical framework for magnon manipulation based on ferroelectric polarization switching in two-dimensional multiferroics. Taking monolayer multiferroics $\mbox{Ti}_{2}\mbox{F}_{3}$ as an example, our calculations demonstrate that ferroelectric switching can significantly modulate spin exchanges, thereby enabling nonvolatile and reversible electric control of the magnons. More importantly, the ferroelectric polarization reversal leads to a sign change in the Berry curvature, ensuring effective control over the valley Hall and nonlinear Hall response of magnons. This study provides a new way for realizing low-power and electrically controllable magnonic devices.

cond-mat.mtrl-sci↗

arXiv2025

Electro-optic effects in some sliding ferroelectrics

Sliding ferroelectrics, which exhibit out-of-plane polarization arising from specific stacking rather than conventional ionic displacements, are new types of ferroelectrics whose underdeveloped physics needs to be explored. Here, we investigate the electro-optic (EO) response of these materials using first-principles calculations, focusing on ZrI$_{2}$ as a prototype. We reveal that, contrary to conventional ferroelectrics, the EO effect in ZrI$_{2}$ is dominated by its electronic contribution rather than the ionic one, which promises faster EO responses. Furthermore, both biaxial and uniaxial strains significantly enhance this response, and a universal-like linear relationship between the band gap and such response is discovered. We also report a large elasto-optic coefficient that is independent of biaxial strain. Similar large linear EO coefficients and properties are found in other sliding ferroelectrics, including different zirconium dihalides, as well as BN and BP bilayers. These findings highlight sliding ferroelectrics as highly promising candidates for ultrafast nonlinear optical devices and reveal unusual mechanisms.

cond-mat.mtrl-sci↗

arXiv2025

Nonreciprocal magnons in layered antiferromagnets VPX3(X =S,Se,Te)

Nonreciprocal magnons, characterized by propagation with differing energies along the k and -k directions, are crucial for modern spintronics applications. However, their realization in van der Waals layered antiferromagnets remains elusive. In this letter, we report robust nonreciprocal magnon behavior in layered honeycomb antiferromagnets VPX3(X =S,Se,Te). Our results demonstrate that, in addition to their intrinsic Dzyaloshinskii-Moriya interaction (DMI), the nonreciprocity of magnons is strongly influenced by the layer number, interlayer coupling, and magnon-magnon interactions. More importantly, in such layered antiferromagnets, the magnon nonreciprocity exhibits an asymmetric periodic dependence on the Neel vector, offering a novel route for experimentally probing antiferromagnetic order parameters in the 2D limit.

cond-mat.mtrl-sci↗

arXiv2025

Topological switching in bilayer magnons via electrical control

Topological magnons, quantized spin waves featuring nontrivial boundary modes, present a promising route toward lossless information processing. Realizing practical devices typically requires magnons excited in a controlled manner to enable precise manipulation of their topological phases and transport behaviors. However, their inherent charge neutrality and a high frequency nature pose a significant challenge for nonvolatile control, especially via electric means. Herein, we propose a general strategy for electrical control of topological magnons in bilayer ferromagnetic insulators. With strong spin-layer coupling, an applied vertical electric field induces an interlayer potential imbalance that modifies intralayer Heisenberg exchanges between adjacent layers. This electric-field-driven modulation competes with the bilayer's intrinsic Dzyaloshinskii-Moriya interaction, enabling the accurate tuning of the band topology and nonreciprocal dynamics of magnons. More importantly, such an electric control mechanism exhibits strong coupling with external magnetic fields, unveiling new perspectives on magnetoelectric coupling in charge-neutral quasiparticles

cond-mat.mes-hall↗

arXiv2025

Nonvolatile Magnonics in Bilayer Magnetic Insulators

Nonvolatile control of spin order or spin excitations offers a promising avenue for advancing spintronics; however, practical implementation remains challenging. In this letter, we propose a general framework to realize electrical control of magnons in 2D magnetic insulators. We demonstrate that in bilayer ferromagnetic insulators with strong spin-layer coupling, electric field Ez can effectively manipulate the spin exchange interactions between the layers, enabling nonvolatile control of the corresponding magnons. Notably, in this bilayer, Ez can induce nonzero Berry curvature and orbital moments of magnons, the chirality of which are coupled to the direction of Ez. This coupling facilitates Ez manipulate the corresponding magnon valley and orbital Hall currents. Furthermore, such bilayers can be easily engineered, as demonstrated by our density-functional-theory calculations on Janus bilayer Cr-based ferromagnets. Our work provides an important step toward realizing nonvolatile magnonics and paves a promising way for future magnetoelectric coupling devices.

cond-mat.mtrl-sci↗

arXiv2024

Giant electro-optic and elasto-optic effects in ferroelectric NbOI$_{2}$

First-principles calculations are performed to investigate the electro-optic (EO) and elasto-optic effects of the three-dimensional (bulk) and two-dimensional (monolayer) ferroelectric NbOI$_{2}$. Remarkably large linear EO and elasto-optic coefficients are discovered in both systems, when under stress-free conditions. We further found that the EO responses of bulk and monolayer NbOI$_{2}$ can be further enhanced with epitaxial strain, because of a strain-driven ferroelectric-to-paraelectric transition that originates from the softening of some polar optical modes. Our findings thus point out that NbOI$_{2}$, as well as other niobium oxide dihalides are highly promising for paving the way for potentially efficient nonlinear optical device applications.

cond-mat.mtrl-sci↗

arXiv2024

Strain-induced bent domains in ferroelectric nitrides

Ferroelectric nitrides have emerged as promising semiconductor materials for modern electronics. However, their domain structures and associated properties are basically unknown, despite their potential to result in optimized or new phenomena. Density functional theory calculations are performed to investigate the effect of epitaxial strain on multidomains of (Al,Sc)N nitride systems and to compare it with the monodomain case. The multidomain systems are predicted to have five strain-induced regions, to be denoted as Regions I to V, respectively. Each of these regions is associated with rather different values or behaviors of physical properties such as axial ratio, polarizations, internal parameters, bond lengths, etc. Of particular interest is the prediction of bent domains under compressive strain extending beyond $-$5.5%, which indicates that domain walls may play a key role in the mechanical failure properties of these systems. Interestingly, such bending induces the creation of a finite in-plane polarization (in addition to out-of-plane dipoles) due to geometric and symmetry considerations. Strikingly too, the bent domains have lower energy than the wurtzite monodomains and have atomically sharp boundaries. Our findings may pave the way for domain wall engineering in ferroelectric nitrides.

cond-mat.mtrl-sci↗

arXiv2024

Electro-optic properties from ab initio calculations in two-dimensional materials

Electro-optic (EO) effects relate the change of optical constants by low-frequency electric fields. Thanks to the advent of Density Functional Perturbation Theory (DFPT), the EO properties of bulk three-dimensional (3D) materials can now be calculated in an ab initio way. However, the use of periodic boundary conditions in most Density Functional Theory codes imposes to simulate two-dimensional (2D) materials using slabs surrounded by a large layer of vacuum. The EO coefficients predicted from such calculations, if not rescaled properly, can severely deviate from the real EO properties of 2D materials. The present work discusses the issue and introduces the rescaling relationships allowing to recover the true EO properties.

cond-mat.mtrl-sci↗

arXiv2023

Energy storage properties of ferroelectric nanocomposites

An atomistic effective Hamiltonian technique is used to investigate the finite-temperature energy storage properties of a ferroelectric nanocomposite consisting of an array of BaTiO$_{3}$ nanowires embedded in a SrTiO$_{3}$ matrix, for electric field applied along the long axis of the nanowires. We find that the energy density \textit{versus} temperature curve adopts a nonlinear, mostly temperature-independent response when the system exhibits phases possessing an out-of-plane polarization and vortices while the energy density more linearly increases with temperature when the nanocomposite either only possesses vortices (and thus no spontaneous polarization) or is in a paraelectric and paratoroidic phase for its equilibrium state. Ultrahigh energy density up to $\simeq$140 J/cm$^{3}$ and an ideal 100% efficiency are also predicted in this nanocomposite. A phenomenological model, involving a coupling between polarization and toroidal moment, is further proposed to interpret these energy density results.

cond-mat.mtrl-sci↗

arXiv2021

Energy storage in lead-free Ba(Zr, Ti)O$_{3}$ relaxor ferroelectrics: Large densities and efficiencies and their origins

An atomistic first-principles-based effective Hamiltonian is used to investigate energy storage in Ba(Zr$_{0.5}$Ti$_{0.5}$)O$_{3}$ relaxor ferroelectrics, both in their bulk and epitaxial films' forms, for electric fields applied along different crystallographic directions. We find that the energy density linearly increases with temperature for electric fields applied along the pseudocubic [001], [110] and [111] directions in Ba(Zr$_{0.5}$Ti$_{0.5}$)O$_{3}$ bulk. For films at room temperature, the energy density adopts different behaviors (i.e., increase versus decrease) with strain depending on the direction of the applied electric fields. We also predicted ultrahigh energy densities (basically larger than 100 J/cm$^{3}$) with an ideal efficiency of 100\% in all these Ba(Zr$_{0.5}$Ti$_{0.5}$)O$_{3}$ systems. In addition, a phenomenological model is used to reveal the origin of all the aforementioned features, and should be applicable to other relaxor ferroelectrics.

cond-mat.mtrl-sci↗

arXiv2021

Ultrahigh energy storage density in epitaxial AlN/ScN superlattices

Dielectric and antiferroelectric materials are particularly promising for high-power energy-storage applications. However, relatively low energy density greatly hinders their usage in storage technologies. Here, we report first-principles-based calculations predicting that epitaxial and initially non-polar AlN/ScN superlattices can achieve an ultrahigh energy density of up to 200 J/cm$^{\textrm{3}}$, accompanied by an ideal efficiency of 100%. We also show that high energy density requires the system being neither too close nor too far from a ferroelectric phase transition under zero electric field. A phenomenological model is further proposed to rationalize such striking features.

cond-mat.mtrl-sci↗

arXiv2021

Electrocaloric effects in multiferroics

An atomistic effective Hamiltonian is used to compute electrocaloric (EC) effects in rare-earth substituted BiFeO$_{3}$ multiferroics. A phenomenological model is then developed to interpret these computations, with this model indicating that the EC coefficient is the sum of two terms, that involve electric quantities (polarization, dielectric response), the antiferromagnetic order parameter, and the coupling between polarization and antiferromagnetic order. The first one depends on the polarization and dielectric susceptibility, has the analytical form previously demonstrated for ferroelectrics, and is thus enhanced at the ferroelectric Curie temperature. The second one explicitly involves the dielectric response, the magnetic order parameter and a specific magnetoelectric coupling, and generates a peak of the EC response at the Néel temperature. These atomistic results and phenomenological model may be put in use to optimize EC coefficients.

cond-mat.mtrl-sci↗

arXiv2020

Linear versus nonlinear electro-optic effects in materials

Two schemes are proposed to compute the nonlinear electro-optic (EO) tensor for the first time. In the first scheme, we compute the linear EO tensor of the structure under a finite electric field, while we compute the refractive index of the structure under a finite electric field in the second scheme. Such schemes are applied to Pb(Zr,Ti)O$_{3}$ and BaTiO$_{3}$ ferroelectric oxides. It is found to reproduce a recently observed feature, namely why Pb(Zr$_{0.52}$Ti$_{0.48}$)O$_{3}$ adopts a mostly linear EO response while BaTiO$_{3}$ exhibits a strongly nonlinear conversion between electric and optical properties. Furthermore, the atomistic insight provided by the proposed ab-initio scheme reveals the origin of such qualitatively different responses, in terms of the field-induced behavior of the frequencies of some phonon modes and of some force constants.

cond-mat.mtrl-sci↗

arXiv2018

Giant electrocaloric response in the prototypical Pb(Mg,Nb)O$_{3}$ relaxor ferroelectric from atomistic simulations

An atomistic effective Hamiltonian is used to investigate electrocaloric (EC) effects of Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$ (PMN) relaxor ferroelectrics in its ergodic regime, and subject to electric fields applied along the pseudocubic [111] direction. Such Hamiltonian qualitatively reproduces (i) the electric field-versus-temperature phase diagram, including the existence of a critical point where first-order and second-order transitions meet each other; and (ii) a giant EC response near such critical point. It also reveals that such giant response around this critical point is microscopically induced by field-induced percolation of polar nanoregions. Moreover, it is also found that, for any temperature above the critical point, the EC coefficient-versus-electric field curve adopts a maximum (and thus larger electrocaloric response too), that can be well described by the general Landau-like model proposed in [Jiang et al, Phys. Rev. B 96, 014114 (2017)] and that is further correlated with specific microscopic features related to dipoles lying along different rhombohedral directions. Furthermore, for temperatures being at least 40 K higher than the critical temperature, the (electric field, temperature) line associated with this maximal EC coefficient is below both the Widom line and the line representing percolation of polar nanoregions.

cond-mat.mtrl-sci↗