arXiv subjects

Baibiao Huang

Publications and source records attributed to Baibiao Huang.

At least 19 recordsLinked to original sources

arXiv2026

Symmetry-Enforced Ferroelectric Switching of Two-Dimensional Altermagnetism

Altermagnetism features strong momentum-dependent spin splitting despite zero net magnetization, offering a transformative platform for next-generation spintronics. However, the nonvolatile and deterministic switching between its two equivalent spin-splitting states remains a fundamental bottleneck. Here, we propose a universal layer-engineering paradigm to achieve symmetry-enforced ferroelectric switching of two-dimensional altermagnetism. By sandwiching a conventional antiferromagnetic monolayer between two identical ferroelectric layers, the out-of-plane polarization cleanly breaks the spatial symmetry to induce robust altermagnetic splitting. Crucially, the global combined parity-time symmetry dictates that reversing the ferroelectric polarization exactly inverts the altermagnetic spin-splitting pattern. We rigorously validate this mechanism in the In2Se3/MnPTe3/In2Se3 trilayer using first-principles calculations. As a direct consequence, the ferroelectrically driven spin-splitting reversal deterministically flips the anomalous Hall effect signal, providing an unambiguous transport fingerprint to electrically distinguish the two altermagnetic states. Unconstrained by the stringent symmetry requirements of intrinsic single-phase materials, our findings establish a versatile physical framework for electrically addressable altermagnetic spintronics.

cond-mat.mtrl-sci↗

arXiv2026

Floquet-Engineered Odd-Parity Altermagnetic Higher-Order Topology in a Two-Dimensional Antiferromagnet Cr$_2$CH$_2$

Periodic driving provides a platform to dynamically tailor quantum states of matter, yet its impact on symmetry-protected topological phases remains incompletely understood. Here, we demonstrate that periodic driving enables the realization of an odd-parity altermagnetic (AM) higher-order topological insulator (HOTI) phase in the Cr$_2$CH$_2$ monolayer. In equilibrium, Cr$_2$CH$_2$ is a 2D antiferromagnetic (AFM) HOTI protected by $\mathcal C_3$ rotational symmetry, characterized by a symmetry indicator $χ^{(3)}$ = $\{-2,1\}$ and robust corner states. Under circularly polarized light (CPL), the system develops a f-wave altermagnetic state governed by the symmetry $[C_{2}||\overline{3}_{001}]$ with odd-parity spin splitting. Despite substantial Floquet-induced band renormalization, the $\mathcal C_3$-protected corner states remain intact over a broad range of driving strengths, highlighting the altermagnetic higher-order topology under Floquet driving. As the light intensity increases, the system gradually evolves into an altermagnetic semimetallic state. These results establish a direct connection between magnetism and topology in a periodically driven AFM system, offering a route toward the control of coupled spin and topological transport.

physics.comp-ph↗

arXiv2026

Second-order topology in two-dimensional azulenoid kekulene carbon lattices

The discovery of higher-order topological insulator (HOTI) has established a new paradigm for understanding symmetry-constrained boundary electronic states. Here, based on first-principles calculations, we demonstrate the emergence of HOTI phase in organic lattices of two-dimensional azulenoid-kekulene-type carbon allotropes, namely AKC-[3,3] and AKC-[6,0]. Enabled by the $C_6$ rotational symmetry, the nontrivial bulk topology is confirmed through the topological invariant and fractionally quantized corner charge, giving $\{[M^{(I)}_{2}],[K^{(3)}_{2}]\}$ = $\{0,2\}$ and $Q_{\mathrm{corner}} = e/3$, respectively, accompanied by the emergence of exotic corner states in nanoflakes. Notably, the structural modifications are explored, revealing that in the derived structure PAK-[6,0], whose corner-localized states are preserved, highlighting the robustness of the higher-order topological phase. These findings highlight azulenoid-kekulene-based carbon allotropes as a promising platform to explore the interplay between structural design, crystalline symmetry, and higher-order topological boundary responses in two dimensional carbon systems.

cond-mat.mtrl-sci↗

arXiv2026

Symmetry-dictated switching of antiferromagnetic magnon transport in 2D multiferroics

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.

cond-mat.mtrl-sci↗

arXiv2026

Symmetry-Driven Electrical Switching of Anisotropic Skyrmion Hall Effect in Altermagnets

Controlling the skyrmion Hall effect (SkHE) is pivotal for developing topological spintronics but typically relies on magnetic field reversal. Here, we demonstrate a general strategy for the purely electrical switching of the SkHE in two-dimensional altermagnets. Through symmetry and model analysis, we reveal that the intrinsic altermagnetic symmetry imposes sublattice-dependent anisotropic exchange and Dzyaloshinskii-Moriya interactions. These interactions induce a highly anisotropic SkHE, where the transverse velocity is strictly dictated by the current direction relative to the crystal axes. Crucially, we show that an external electric field can strongly modulate these interaction parameters by inversing the altermagnetic symmetry, allowing for the reversible inversion of the anisotropic SkHE. Using first-principles and atomistic spin model simulations, this mechanism is further demonstrated in monolayer CaMnSn. Our study establishes a unique strategy for realizing precise, electrically tunable skyrmion transport without magnetic fields.

cond-mat.mtrl-sci↗

arXiv2026

Design of Skyrmion Bags with Tunable Topology in Symmetry-Broken 2D Lattices

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 propose a novel design principle 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 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 exhibit remarkable thermal stability up to 240 K. Our results provide a compelling platform for exploring high-order topological magnetism.

cond-mat.mtrl-sci↗

arXiv2026

Altermagnetic Skyrmions in 2D Lattices Exhibiting Anisotropic Skyrmion Hall Effect

Anisotropic skyrmion Hall effect (A-SkHE) in two-dimensional (2D) magnetic systems represents a captivating phenomenon in condensed-matter physics and materials science. While conventional antiferromagnetic systems inherently suppress this effect through parity-time symmetry-mediated cancellation of Magnus forces acting on skyrmions, A-SkHE is primarily confined to ferromagnetic platforms. Here, we present a paradigm-shifting demonstration of this phenomenon in spin-splitting 2D antiferromagnets through the investigation of altermagnetic skyrmions. Combining comprehensive symmetry analysis with theoretical modeling, we elucidate the mechanism governing A-SkHE realization in 2D altermagnetic systems and establish a quantitative relationship between the transverse velocity of altermagnetic skyrmions and applied current orientation. Using first-principles calculations and micromagnetic simulations, this mechanism is further illustrated in a prototypical altermagnetic monolayer V2SeTeO. Crucially, we identify that the [C2C4zt] symmetry-protected anisotropic field serves as the critical stabilizer for maintaining the A-SkHE in this system. Our results greatly enrich the research on 2D altermagnetism and skyrmions.

cond-mat.mtrl-sci↗

arXiv2026

Ordering Mixed-Q Topological Magnetism into Lattice via Moire Engineering

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. The realization of exotic mixed-Q states, where distinct topological quasiparticles co-assemble into an ordered lattice, remains largely unexplored. Here, we propose a generic mechanism to order disordered mixed-Q topological magnetism into periodic lattice via moire engineering. By leveraging the synergy between spatially modulated interlayer coupling and intrinsic intralayer magnetic frustration, we demonstrate that moire 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 moire potential in stabilizing mixed-Q lattice. Our findings significantly advance the frontier of topological and moire spintronics.

cond-mat.mtrl-sci↗

arXiv2026

Magnonic Quantum Spin Hall Effect with Chiral Magnon Transport in Bilayer Altermagnets

Altermagnetism has attracted considerable interest, yet its associated spintronic phenomena have so far been largely confined to electronic systems. In this work, we uncover a universal symmetry-based strategy for realizing topological altermagnets with the magnonic quantum spin Hall effect, as evidenced by a nonzero spin Chern number and protected helical edge states. Moreover, we demonstrate that chiral magnon splitting in altermagnets gives rise to an intrinsically anisotropic, momentum-resolved thermal Hall response, sharply contrasting with those in ferromagnets and antiferromagnets, thus offering enhanced flexibility for selective manipulation. As a concrete material realization, first-principles calculations and Heisenberg-DM model analysis reveal that V$_2$WS$_4$ bilayer exhibits $d$-wave altermagnetism, integer spin Chern number with helical magnon edge states, and the nonzero momentum-locked thermal Hall conductivity. Our results establish a direct link between topological magnons and altermagnetism, opening new avenues for dissipationless magnonic devices.

cond-mat.mtrl-sci↗

arXiv2025

Light-Induced Spin Slanting in 2D Multiferroic Magnet

Controlling spin orientation of two-dimensional (2D) materials has emerged as a frontier of condensed-matter physics, resulting in the discovery of various phases of matter. However, in most cases, spin orientation can be stablished only at specific directions of out-of-plane and in-plane, which is a drawback compared with three-dimensional systems, limiting exploration of novel physics. Here, we introduce a methodology for manipulating spin slanting in 2D multiferroic materials through ultrafast pulses of light. Based on model analysis, we find that simultaneous triggering spin-orbit coupling induced interactions from in-plane and out-of-plane orbitals can generate spin slanting. By choosing 2D multiferroic materials with specific low-energy composition endowed by symmetry, such triggering can be readily achieved through ultrafast light illumination, leading to light-induced spin slanting. Using real-time time-dependent density-functional theory, we demonstrate this approach in multiferroic single-layer CuCr2Se4. This study provides an efficient way to manipulate spin orientation in 2D materials and establishes a general platform to explore physics and applications associated with spin slanting.

cond-mat.mes-hall↗

arXiv2024

Ultrafast laser driven ferromagnetic-antiferromagnetic skyrmion switching in 2D topological magnet

Light-spin coupling is an attractive phenomenon from the standpoints of fundamental physics and device applications, and has spurred rapid development recently. Whereas the current efforts are devoted to trivial magnetism, the interplay between light and nontrivial spin properties of topological magnetism is little known. Here, using first principles, rt-TDDFT and atomic spin simulations, we explore the evaluation of topological spin properties of monolayer CrInSe3 under laser, establishing the ultrafast ferromagnetic-antiferromagnetic skyrmion reversal. The physics correlates to the laser-induced significant spin-selective charge transfer, demagnetization, and time-dependent magnetic interactions. Especially, an essential switching from ferromagnetic to antiferromagnetic exchange is generated under light irradiation. More importantly, dynamics of topological magnetic physics shows that this process accompanies with the evaluation of topological magnetism from ferromagnetic to antiferromagnetic skyrmions, manifesting intriguing interplay between light and topological spin properties. Our letter provides a novel approach toward the highly desired ultrafast control of topological magnetism.

cond-mat.mtrl-sci↗

arXiv2024

Ferro-Valleytricity with In-Plane Magnetization

Ferro-valleytricity, a fundamental phenomenon that manifests spontaneous valley polarization, is generally considered to occur in two-dimensional (2D) materials with out-of-plane magnetization. Here, we propose a mechanism to realize ferro-valleytricity in 2D materials with in-plane magnetization, wherein the physics correlates to non-collinear magnetism in triangular lattice. Our model analysis provides comprehensive ingredients that allows for in-plane ferro-valleytricity, revealing that mirror symmetry is required for remarkable valley polarization and time-reversal-mirror joint-symmetry should be excluded. Through modulating in-plane magnetization offset, the valley polarization could be reversed. Followed by first-principles, such mechanism is demonstrated in a multiferroic triangular lattice of single-layer W3Cl8. We further show that the reversal of valley polarization could also be driven by applying electric field that modulates ferroelectricity. Our findings greatly enrich the valley physics research and significantly extend the scope for material classes of ferro-valleytricity.

cond-mat.mtrl-sci↗

arXiv2024

Small exciton effective mass in QL Bi2Se2Te: A material platform towards high-temperature excitonic condensate

Using first-principles simulations combined with many-body calculations, we show that two-dimensional free-standing quintuple-layer Bi2Se2Te is an inversion symmetric monolayer expected to achieve spatially indirect exciton with large exciton radius, small exciton effective mass and long exciton lifetime. Such system is theoretically predicted to be a promising platform for realizing excitonic Bose-Einstein condensation and superfluid due to its high phase transition temperatures of ~257 K and ~64.25 K for the BEC and excitonic superfluid, respectively. The importance of spin-orbit coupling is revealed, and the angular momentum selection rules for photon absorption are discussed. This finding suggests the potential of QL Bi2Se2Te monolayer with exotic bosonic bound states provides as a tantalizing high-temperature platform to probe excitonic physics.

cond-mat.mtrl-sci↗

arXiv2024

Coupling multi-space topologies in 2D ferromagnetic lattice

Topology can manifest topological magnetism (e.g., skyrmion and bimeron) in real space and quantum anomalous Hall (QAH) state in momentum space, which have changed the modern conceptions of matter phase. While the topologies in different spaces are widely studied separately, their coexistence and coupling in single phase is seldomly explored. Here, we report a novel phenomenon that arises from the interaction of topological magnetism and band topology, the multi-space topology, in 2D ferromagnetic lattice. Based on continuum theory and tight-binding model, we reveal that the interconnection between skyrmion/bimeron and QAH state generates distinctive localized chiral bound states (CBSs). With moderating topological magnetism through magnetic field, the multi-space topologies accompanied with different CBSs can be reversed, facilitating the coupling of multi-space topologies. By performing firstprinciples and atomic spin model simulations, we further demonstrate such multi-space topologies and their coupling in monolayer Cr2NSb. These results represent an important step towards the development of multispace topological phenomena in 2D lattice.

cond-mat.mtrl-sci↗

arXiv2024

Ferroelectrovalley in Two-Dimensional Multiferroic Lattices

Engineering valley index is essential and highly sought for valley physics, but currently it is exclusively based on the paradigm of the challenging ferrovalley with spin-orientation reversal under magnetic field. Here, an alternative strategy, i.e., the so-called ferroelectrovalley, is proposed to tackle the insurmountable spin-orientation reversal, which reveres valley index with the feasible ferroelectricity. Using symmetry arguments and tight-binding model, the C_2 rotation is unveiled to be able to take the place of time reversal for operating valley index in two-dimensional multiferroic kagome lattices, which enables the ferroelectricity-engineered valley index, thereby generating the concept of ferroelectrovalley. Based on first-principles calculations, this concept is further demonstrated in the breathing kagome lattice of single-layer Ti3Br8, wherein ferroelectricity couples the breathing process. These findings open a new direction for valleytronics and two-dimensional materials research.

cond-mat.mtrl-sci↗

arXiv2024

Topology-engineered orbital Hall effect in two-dimensional ferromagnets

Recent advances in manipulation of orbital angular momentum (OAM) within the paradigm of orbitronics present a promising avenue for the design of future electronic devices. In this context, the recently observed orbital Hall effect (OHE) occupies a special place. Here, focusing on both the second-order topological and quantum anomalous Hall insulators in two-dimensional ferromagnets, we demonstrate that topological phase transitions present an efficient and straightforward way to engineer the OHE, where the OAM distribution can be controlled by the nature of the band inversion. Using first-principles calculations, we identify Janus RuBrCl and three septuple layers of MnBi$_2$Te$_4$ as experimentally feasible examples of the proposed mechanism of OHE engineering by topology. With our work we open up new possibilities for innovative applications in topological spintronics and orbitronics.

cond-mat.mtrl-sci↗

arXiv2023

Bloch-type magnetic skyrmions in two-dimensional lattice

Magnetic skyrmions in two-dimensional lattice are a prominent topic of condensed matter physics and material science. Current research efforts in this field are exclusively constrained to Neel-type and antiskyrmion, while Bloch-type magnetic skyrmions are rarely explored. Here, we report the discovery of Bloch-type magnetic skyrmions in two-dimensional lattice of MnInP2Te6, using firstprinciples calculations and Monte-Carlo simulations. Arising from the joint effect of broken inversion symmetry and strong spin-orbit coupling, monolayer MnInP2Te6 presents large Dzyaloshinskii-Moriya interaction. This, along with ferromagnetic exchange interaction and out-ofplane magnetic anisotropy, gives rise to skyrmion physics in monolayer MnInP2Te6, without needing magnetic field. Remarkably, different from all previous works on two-dimensional lattice,the resultant magnetic skyrmions feature Bloch-type, which is protected by D3 symmetry.Furthermore, the Bloch-type magnetic bimerons are also identified in monolayer MnTlP2Te6. The phase diagrams of these Bloch-type topological magnetisms under magnetic field, temperature and strain are mapped out. Our results greatly enrich the research on magnetic skyrmions in twodimensional lattice.

cond-mat.mtrl-sci↗

arXiv2022

Ferroelectric higher-order topological insulator in two dimensions

The interplay between ferroelectricity and band topology can give rise to a wide range of both fundamental and applied research. Here, we map out the emergence of nontrivial corner states in two-dimensional ferroelectrics, and remarkably demonstrate that ferroelectricity and corner states are coupled together by crystallographic symmetry to realize the electric control of higher-order topology. Implemented by density functional theory, we identify a series of experimentally synthesized two-dimensional ferroelectrics, such as In$_2$Se$_3$, BN bilayers, and SnS, as realistic material candidates for the proposed ferroelectric higher-order topological insulators. Our work not only sheds new light on traditional ferroelectric materials but also opens an avenue to bridge the higher-order topology and ferroelectricity that provides a nonvolatile handle to manipulate the topology in next-generation electronic devices.

cond-mat.mtrl-sci↗