Yandong Ma

Antiferromagnetic spintronics promises ultrafast device performance, yet the essential Néel vector reversal is hindered by its intrinsic immunity to external magnetic fields. Here, we propose a mechanism for deterministic Néel vector reversal in 2D van der Waals antiferromagnets enabled by ultrafast laser pulses. The core physics involves light-induced asymmetric interlayer demagnetization, which drives the antiferromagnet into a transient ferrimagnetic state with a finite net moment. This transient symmetry breaking allows the Néel vector to be controlled by an external magnetic field. We identify that the intrinsic structural and electronic asymmetries and spin–orbit-coupling mediated spin flips are essential for this process. Using first-principles calculations and real-time time-dependent density functional theory, we further demonstrate this mechanism in bilayer NiICl and YI2. Our work establishes a general strategy for the optical manipulation of 2D antiferromagnetic order.

Topological magnetic lattices offer a fertile ground for exploring fundamental physics and developing novel spintronic devices. However, current research is predominantly confined to single-Q topologies hosting uniform type of quasiparticle. Here, Q denotes the real-space topological charge of a spin texture, rather than a reciprocal-space ordering wavevector. The realization of exotic mixed-Q states, where distinct topological quasiparticles coassemble into an ordered lattice, remains largely unexplored. Here, we propose a design principle to order disordered mixed-Q topological magnetism into periodic lattice via moiré engineering. By leveraging the synergy between spatially modulated interlayer coupling and intrinsic intralayer magnetic frustration, we demonstrate that moiré potential can effectively regularize skyrmions, antiskyrmions, and magnetic bubbles into a hybrid lattice. Combining first-principles with atomistic spin simulations, we validate this mechanism in twisted bilayer CrGaTe3, identifying it as an exemplary platform for hosting these complex ordered textures. We systematically map the phase evolution as a function of twist angle and biaxial strain, unveiling the critical role of moiré potential in stabilizing mixed-Q lattice. Our findings significantly advance the frontier of topological and moiré spintronics.

Deterministic switching of skyrmion topology is a central frontier in topological spintronics, yet current paradigms rely almost exclusively on dissipative-current-driven spin torques. Here, we propose a fundamentally distinct mechanism for the nonvolatile switching of the skyrmion topology in two-dimensional multiferroics. We reveal that the intrinsic magnetoelectric coupling intimately links the out-of-plane ferroelectric polarization to interlayer magnetic exchange. Consequently, an electric-field-driven polarization reversal deterministically converts the interlayer coupling between the ferromagnetic and antiferromagnetic states. This macroscopic exchange reversal directly flips the microscopic skyrmion core polarity and reverses its topological charge, thereby stabilizing the two electrically addressable topological phases. Guided by our established design principles, we rigorously validate this mechanism in a Co2CF2/MoN2 multiferroic heterostructure by using combined first-principles calculations and atomistic spin simulations. Our findings bypass the limitations of continuous current injection, establishing a robust physical framework for energy-efficient multiferroic topological spintronics.

Altermagnetic multiferroicity is rapidly emerging as a transformative paradigm for both condensed matter physics and advanced spintronics. However, existing magnetoelectric mechanisms are inherently restricted to structural inversions, which merely reverse the momentum‐space spin splitting. Here, guided by symmetry principles and microscopic modeling, we unveil an emergent class of altermagnetic multiferroicity in 2D heterobilayers. This mechanism utilizes out‐of‐plane ferroelectric polarization to govern the interlayer coupling, thereby tuning the competition between localized antiferromagnetic superexchange and itinerant ferromagnetic double‐exchange. Crucially, this interfacial modulation triggers a reversible magnetic phase transition between a trivial ferromagnetic state and an altermagnetic state, establishing a distinct magnetoelectric coupling mechanism. Using first‐principles calculations, we demonstrate this mechanism in MnPS ₃ /Sc ₂ CO ₂ heterostructure, where we further predict the emergence of two distinct altermagnetic phases. Our findings transcend geometric restrictions, establishing a physical framework for nonvolatile and programmable altermagnetic spintronics.

While antiferromagnetic magnons in two-dimensional (2D) materials hold immense promise for high-frequency spintronics, achieving their efficient active control remains a critical challenge. Here, we propose a universal mechanism for the nonvolatile ferroelectric (FE) switching of antiferromagnetic magnon transport in 2D multiferroic lattices. Our mechanism relies on coupling the magnon geometric phase to the FE-induced sublattice asymmetry in exchange and Dzyaloshinskii-Moriya interactions. This explicitly breaks the exact compensation of opposite-chirality magnons inherent to collinear antiferromagnets, lifting their spin degeneracy and inducing a highly tunable net Berry curvature. Crucially, reversing the FE polarization deterministically swaps these magnetic asymmetries, which completely inverts the net magnon Berry curvature and the resulting anomalous thermal Hall conductivity. Using first-principles and linear spin-wave theory, we rigorously validate this geometric-phase-driven mechanism in single-layer CuCr2Se4. Our findings establish a robust paradigm for coupling multiferroicity with the magnon geometric phase, paving the way for nonvolatile and electrically switchable antiferromagnetic magnonics.

Light–spin interactions attract a great deal of interest both for their fundamental physics and for their potential applications. Despite substantial theoretical and experimental efforts, inducing magnetization in intrinsically nonmagnetic systems using linearly polarized light constitutes a critically underdeveloped research frontier. Here, we propose a novel mechanism for generating light-induced magnetization in nonmagnetic van der Waals heterobilayers under linearly polarized light. Our mechanism emerges from the synergistic interplay between light-driven nonequilibrium carrier dynamics and electronic instabilities associated with van Hove singularities. Specifically, ultrafast linearly polarized light creates nonequilibrium carriers near the van Hove singularities, promoting spin-flip processes mediated by spin–orbit coupling during carrier relaxation, which subsequently triggers remarkable spin polarization. Using a combination of first-principles calculations and real-time time-dependent density functional theory, we further confirm this paradigm in the InS/GaSe heterobilayer. Our findings open a new direction for research on light–spin interactions.

Magnetic skyrmion bags, as high-order topological swirling spin textures, offer rich fundamental physics and distinct advantages for spintronic applications; however, their realization remains a formidable challenge, especially in two-dimensional (2D) systems. Here, through model analysis, we establish a theoretical framework for engineering skyrmion bags with tunable topology in symmetry-broken 2D ferromagnetic lattices. The physics correlates to the delicate interplay of isotropic exchange interaction, Dzyaloshinskii-Moriya interaction, and magnetic anisotropy, which can stabilize a rich variety of high-order topological spin states as well as the intriguing skyrmionium with zero topological charge. We further validate this mechanism in monolayer CrInTe₂ by using first-principles calculations and atomistic spin model simulations, revealing the existence of field-free skyrmion bags. Furthermore, we find that a weak magnetic field triggers a transition to skyrmioniums that maintains their structural integrity up to 240 K. Our results provide a compelling platform for exploring the high-order topological magnetism.

The search for multiferroicity in two-dimensional (2D) systems has predominantly focused on spin-driven mechanisms, leaving the distinct physics of coupled spin-orbital orders largely unexplored. Here, we propose a theoretical mechanism for orbital multiferroicity on 2D triangular lattices, arising from the intrinsic interplay between ferro-orbital and magnetic orders. Through symmetry analysis and effective model derivation, we reveal that the orbital order imposes a strong interaction on the magnetic sector, activating robust orbiton-magnon hybridization. Using density-functional theory calculations, we substantiate this mechanism in monolayer FeH_{2}, where cooperative orbital and spin interactions stabilize an antiferro-orbital antiferromagnetic ground state. Remarkably, mechanical strain efficiently tunes these interactions, enabling reversible phase transitions between the antiferro-orbital and ferro-orbital states. Crucially, the elementary excitation spectrum exhibits hybridization gaps, serving as a definitive fingerprint of the formed entangled magnon-orbiton modes. Our Letter thus establishes a novel paradigm for exploring orbital multiferroicity in 2D systems.

Triferroicity in two‐dimensional (2D) materials provides an exceptional platform for multifunctional devices, yet combining a spin‐splitting antiferromagnetic (AFM) state with ferroelectricity and ferroelasticity remains a formidable challenge. Here, we propose a general strategy to achieve concurrent ferroelectricity, AFM spin splitting, and ferroelasticity by incorporating superatoms into 2D lattices. We show that strong p‐d orbital hybridization induces spontaneous symmetry‐lowering distortions of superatoms, breaking inversion symmetry and stabilizing magnetic ordering. This mechanism enables the coexistence of these three ferroic orders—an effect that is difficult to achieve with conventional atomic building blocks. Using first‐principles calculations, we identify the NbB ₁₂ H ₆ monolayer as a representative example, in which the Jahn‐Teller effect drives the structural distortion. Crucially, reversing the ferroelectric polarization in the NbB ₁₂ H ₆ leads to a deterministic reversal of the AFM spin splitting, demonstrating robust magnetoelectric coupling. Moreover, this superatom‐based multiferroic framework can be readily extended to a broad class of materials through the incorporation of alternative metals or superatomic motifs. Our findings establish superatom assembly as a powerful paradigm for designing 2D multiferroics with controllable spin degrees of freedom.