arXiv subjects

Zhong Shen

Publications and source records attributed to Zhong Shen.

11 recordsLinked to original sources

arXiv2026

Antitopological magnetic textures in an antiferromagnetically coupled bilayer with frustration

The bilayer skyrmion composed of upper and lower tightly coupled skyrmions on two layers with completely compensated topological charges (called as anti-topology here), has become one feasible improvement of conventional skyrmion to realize straight motion without skyrmion Hall effect, which has aroused great interest in practical applications. The present work investigates a general model (without external magnetic field) for the frustration-induced anti-topological bilayer magnetic textures with rich morphologies, and discusses the modulations of key parameters on the energy barrier and the current-driven dynamics. It is revealed that the interlayer coupling plays a key role in preventing distortion, and thus helps to reach a faster velocity. This model can be realized in various frustrated magnetic materials with antiferromagnetically coupled bilayer, providing a helpful guidance for the material design and application of topological magnetic textures.

cond-mat.mes-hall↗

arXiv2026

Magnetoelectric torque in polar magnetic bilayers

Energy-efficient fast switching of spin orientations or textures is a core issue of spintronics, which is highly demanded but remains challenging. Different from the mainstream routes based on spin-transfer torque or spin-orbit torque, here we propose another mechanism coined as magnetoelectric torque to switch the magnetization in polar magnetic bilayers via pure electric field. In some magnetic van der Waals bilayers, when the electrostatic energy of polarization can compensate the interlayer magnetic coupling, a magnetoelectric torque is generated to fastly flip spins within a few picoseconds, which is demonstrated by combining the first-principles calculations, analytic model, as well as atomistic simulations. Such a magnetoelectric torque doesn't rely on the spin-orbit coupling and is generally active in polar magnetic homostructures and heterostructures. Our work provides an alternative route to switch magnetization in nanoscale, which may benefit the energy-saving and fast-response spintronic devices.

cond-mat.mtrl-sci↗

arXiv2025

Crescent domain-wall pairs in anisotropic two-dimensional MnOI monolayer with fast dynamics

The controllable and efficient manipulation is always a key challenge for the application of topological magnetic textures in spintronic devices. By first-principles calculations and atomistic simulations, the present work reveals an exotic domain-wall pair in crescent shape, which possesses topology in one dimension and particle-like robustness in two dimensions. Its antiferromagnetic version is observed in the two-dimensional MnOI monolayer with a strong anisotropy, and the ferromagnetic version exists under an appropriate strain. Both of them can be driven efficiently by current to move in a straight line along a certain direction. Hereby, another possible path is provided to realize the application of topological magnetic texture in the next-generation high-speed spintronic devices.

cond-mat.mtrl-sci↗

arXiv2024

Noncollinear ferroelectric and screw-type antiferroelectric phases in a metal-free hybrid molecular crystal

Noncollinear dipole textures greatly extend the scientific merits and application perspective of ferroic materials. In fact, noncollinear spin textures have been well recognized as one of the core issues of condensed matter, e.g. cycloidal/conical magnets with multiferroicity and magnetic skyrmions with topological properties. However, the counterparts in electrical polarized materials are less studied and thus urgently needed, since electric dipoles are usually aligned collinearly in most ferroelectrics/antiferroelectrics. Molecular crystals with electric dipoles provide a rich ore to explore the noncollinear polarity. Here we report an organic salt (H2Dabco)BrClO4 (H2Dabco = N,N'-1,4-diazabicyclo[2.2.2]octonium) that shows a transition between the ferroelectric and antiferroelectric phases. Based on experimental characterizations and ab initio calculations, it is found that its electric dipoles present nontrivial noncollinear textures with $60^\circ$-twisting angle between the neighbours. Then the ferroelectric-antiferroelectric transition can be understood as the coding of twisting angle sequence. Our study reveals the unique science of noncollinear electric polarity.

cond-mat.mtrl-sci↗

arXiv2024

Magnetoelectric imprint of skyrmions in van der Waals bilayers

To effectively track and manipulate topological solitons (e.g. skyrmions) are the key challenge before their applications. Inspired by the idea of sliding ferroelectricity, here a general strategy is proposed to print magnetic skyrmions to electric skyrmions in van der Waals bilayers. Through the proximate interactions, there is an isoperiodic bijection relationship between local dipoles and spin moments. This magnetoelectric imprint effect not only extends the strategies to create electric skyrmions, but also leads to an approach for all-electrical readout/manipulation of magnetic skyrmions.

cond-mat.mtrl-sci↗

arXiv2024

High-topological-number skyrmions and phase transition in two-dimensional frustrated $J_1$-$J_2$ magnets

With the rapidly expanded field of two-dimensional(2D) magnetic materials, the frustrated magnetic skyrmions are attracting growing interest recently. Here, based on hexagonal close-packed (HCP) lattice of $J_1$-$J_2$ Heisenberg spins model, we systematically investigate the frustrated skyrmions and phase transition by micromagnetic simulations and first-principles calculations. The results show that four spin phases of antiferromagnetic, labyrinth domain, skyrmion and ferromagnetic textures are determined by the identified ranges of $J_1$-$J_2$. Importantly, skyrmion phase with an increasing topological number ($Q$) covers a wider $J_1$-$J_2$ area. Then, the diameter of skyrmions can be tuned by the frustration strength ($|J_2/J_1|$) or external magnetic field. Besides, a phase transition from N$\acute{e}$el to Bloch type skyrmion is observed due to the change of the helicity with the variation of $|J_2/J_1|$. Furthermore, as increasing magnetic field, the skyrmions with high $Q$ ($\ge 3$) tend to split into the ones with $Q=1$, thereby achieving a lower systematic energy. Additionally, we find that the CoCl$_2$ monolayer satisfies the requirement of the frustrated $J_1$-$J_2$ magnet, and the related magnetic behaviors agree with the above conclusions. The frustration-induced skyrmions are stable without the manipulation of temperature and magnetic field. Our results may open a possible way toward spintronic applications based on High-topological-number and nanoscale topological spin textures of skyrmions.

physics.comp-ph↗

arXiv2023

A Hybrid Advertising Mode for Device Discovery in Bluetooth Low Energy Networks

Device discovery has a great impact on the performance of Bluetooth low energy (BLE). The performance of device discovery is highly related to the advertising mode. BLE has two advertising modes: pseudo-random delay advertising (RDA) and periodic deterministic advertising (PDA). Generally, PDA has low discovery latency but is susceptible to persistent collisions, whereas RDA does not suffer persistent collisions but has much larger discovery latency. In this paper, we propose a novel hybrid advertising mode, called Deterministic and pseudo-Random delay Advertising (DRA), which has the advantages of both PDA and RDA. We develop an analytical model for DRA mode based on a two-dimensional discrete-time Markov chain, and analyze the expected discovery latency of DRA in a single-advertiser case and a multiple-advertiser case. Simulation shows the accuracy of our analytical model, and also verifies that DRA can achieve an excellent tradeoff between low discovery latency and robustness to collisions.

cs.IT↗

arXiv2023

Manipulation of magnetic topological textures via perpendicular strain and polarization in van der Waals magnetoelectric heterostructure

Multi-functional manipulation of magnetic topological textures such as skyrmions and bimerons in energy-efficient ways is of great importance for spintronic applications, but still being a big challenge. Here, by first-principles calculations and atomistic simulations, the creation and annihilation of skyrmions/bimerons, as key operations for the reading and writing of information in spintronic devices, are achieved in van der Waals magnetoelectric CrISe/In2Se3 heterostructure via perpendicular strain or electric field without external magnetic field. Besides, the bimeron-skyrmion conversion, size modulation and the reversible magnetization switching from in-plane to out-of-plane could also be realized in magnetic-field-free ways. Moreover, the topological charge and morphology can be precisely controlled by a small magnetic field. The strong Dzyaloshinskii-Moriya interaction and tunable magnetic anisotropy energy in a wide window are found to play vital roles in such energy efficient multi-functional manipulation, and the underlying physical mechanisms are elucidated. Our work predicts the CrISe/In2Se3 heterostructure being an ideal platform to address this challenge in spintronic applications, and theoretically guides the low-dissipation multi-functional manipulation of magnetic topological textures.

cond-mat.mtrl-sci↗

arXiv2022

Theoretical prediction of Curie temperature in two-dimensional ferromagnetic monolayer

Theoretical prediction of Curie temperature (TC) is of vital importance for designing the spintronic devices in two-dimensional (2D) ferromagnetic materials. Herein, based on the extensive investigation of Monte Carlo simulations, we summary and propose an improved method to estimate TC more precisely, which includes the different contributions of multiple near-neighbor interactions. Taking monolayer CrI3 as an example, the trends of TC with biaxial strain are investigated via Monte Carlo simulations, mean-field formulas and our method. Besides, our method is not only accurate and convenient to predicting the TC in 2D ferromagnetic honeycomb lattice CrI3 but it can be extended for predicting the TC of other 2D lattices. Our work paves the way to accelerate the prediction and discovery of novel 2D ferromagnets for spintronic applications.

cond-mat.mtrl-sci↗

arXiv2022

Strain-tunable Dzyaloshinskii--Moriya interaction and skyrmions in two-dimensional Janus Cr$_{2}$X$_{3}$Y$_{3}$ (X, Y = Cl, Br, I, X $\neq$ Y) trihalide monolayers

Recently, great effort has been devoted to the search for two-dimensional (2D) ferromagnetic materials with inherent strong Dzyaloshinskii--Moriya interaction (DMI). Here, through a first-principles approach, we systematically investigate the effect of biaxial strain on the DMI, the Heisenberg exchange interaction, and the magnetic anisotropy energy (MAE) of Janus Cr$_{2}$X$_{3}$Y$_{3}$ (X, Y = Cl, Br, I, X $\neq$ Y) monolayers. Both DMI and MAE can be significantly enhanced by tensile strain, while a reversal of the chirality of DMI in Cr$_{2}$Cl$_{3}$Br$_{3}$ and a switch of MAE from off-plane to in-plane in Cr$_{2}$I$_{3}$Cl$_{3}$ are induced by a compressive strain of $2\%$. Microscopically, DMI and MAE are associated mainly with the large spin--orbit coupling of the heavy nonmagnetic halogen atoms rather than that of the magnetic Cr atoms. In particular, the peculiar magnetic transition of Cr$_{2}$I$_{3}$Cl$_{3}$ is explained by competition between direct exchange and superexchange interactions. Micromagnetic simulations show that a small external magnetic field of 65~mT stabilizes a skyrmion with a diameter of 9.8~nm in the Cr$_2$I$_3$Cl$_3$ monolayer. Our results will provide guidance for further research on DMI and skyrmions in 2D Janus materials, as well as a basis for the potential applications in spintronic devices.

cond-mat.mtrl-sci↗

arXiv2022

Enhanced Curie temperature and skyrmion stability in room temperature ferromagnetic semiconductor CrISe monolayer

We report CrISe monolayer as a room temperature ferromagnetic semiconductor with the Curie temperature ($T_C$), magnetic anisotropy energy (MAE) and band gap being 322 K, 113 $μ$eV and 0.67 eV, respectively. The $T_C$ and MAE can be further enhanced up to 385 K and 313 $μ$eV by tensile strain. More interestingly, the magnetic easy axis can be switched between off-plane and in-plane by compressive strain. Particularly, due to the broken inversion symmetry and strong spin-orbit coupling of Se atoms, a large Dzyaloshinskii-Moriya interaction (DMI) of 2.40 meV is obtained. More importantly, by micromagnetic simulations, stable skyrmions with sub-10 nm radius are stabilized by the large DMI above room temperature in a wide range of strain from $-2\%$ to $6\%$. Our work demonstrates CrISe as a promising candidate for next-generation skyrmion-based information storage devices and provides guidance for the research of DMI and skyrmions in room temperature ferromagnetic semiconductors.

cond-mat.mtrl-sci↗