arXiv subjects

Sike Zeng

Publications and source records attributed to Sike Zeng.

8 recordsLinked to original sources

arXiv2026

Stacking theory for bilayer two-dimensional magnets

Two-dimensional unconventional magnetism has recently attracted growing interest due to its intriguing physical properties and promising applications in spintronics. However, existing studies on stacking-induced unconventional magnetism mainly focus on specific materials and stacking configurations. Here, we develop a general symmetry-based stacking theory for two-dimensional magnets. We first introduce spin layer groups as the fundamental symmetry framework, providing the essential magnetic symmetry information for the stacking theory. Based on this framework, we construct the complete set of 448 collinear spin layer groups for describing two-dimensional collinear magnets. Subsequently, we develop a general magnetic stacking theory applicable to arbitrary magnetic systems and derive its general solutions. Using CrF$_3$ as an illustrative example, we show how this theory enables designs of two-dimensional unconventional magnetism, as validated by first-principles calculations. We realize two-dimensional fully compensated ferrimagnetism through our stacking theory. Our work provides a general symmetry-guided platform for discovering and designing stacking-induced unconventional magnetism.

cond-mat.mtrl-sci↗

arXiv2026

Classification and design of two-dimensional altermagnets

Altermagnets -- newly identified collinear antiferromagnets -- carry zero net moment with non-relativistic, spin-polarized bands, distilling the best of ferromagnets and antiferromagnets into a single spintronic platform. Shrunking to the two-dimensional limit, they inherit the tunability of two-dimensional crystals while adding symmetry-protected spin splitting, a combination now driving intense experimental interest. Here, we review the symmetry classification of two-dimensional altermagnets based on spin-group theory and survey the growing list of candidate materials, emphasizing those with large spin splitting for experimental realization. We then examine strategies for engineering two-dimensional altermagnetism. This Review aims to consolidate theoretically proposed candidate materials and realization strategies for two-dimensional altermagnets, providing insights for future experimental efforts in this emerging field.

cond-mat.mtrl-sci↗

arXiv2025

Symmetry-guided prediction of magnetic-ordered ground states

Given the scarcity of experimentally confirmed magnetic structures, the prediction of magnetic ground states is crucial yet remains a long-sought challenge due to the complex potential energy landscape. Here, we propose a symmetry-guided framework that systematically generates magnetic configurations without requiring any experimental input or prior assumptions. Within a symmetry-breaking scenario, we incorporate the recently developed oriented spin space group formalism, which captures symmetry-breaking induced by both magnetic ordering and spin-orbit coupling. By performing nonrelativistic and relativistic first-principles calculations, we establish the energy ladder of the generated magnetic configurations. Exemplified by three prominent unconventional magnets, we demonstrate that only a few dozen calculations are sufficient to identify the ground-state magnetic structure. To demonstrate the universality and robustness of our approach, we conduct large-scale benchmark tests on the MAGNDATA database. Our framework successfully reproduces experimentally reported magnetic geometries for 78% of the surveyed materials, among which 93% have their spin orientations successfully generated when considering SOC. Furthermore, in a large-scale first-principles benchmark involving 305 compounds, 82% of experimentally reported magnetic structures are accurately captured within an energy tolerance of 5 meV per magnetic atom. Beyond reproducing known magnetic configurations, our framework further predicts a variety of low-energy metastable phases, including altermagnets, spin-orbit magnets, and noncollinear antiferromagnets with spin splitting or geometric Hall effect. Our work establishes a general and efficient route toward large-scale prediction of magnetic structures and unconventional magnets, and offers insight into the origins of magnetic interactions across diverse material systems.

cond-mat.mtrl-sci↗

arXiv2025

Unlocking Altermagnetism in Antiferromagnetic 2D Films via Adsorption

Altermagnets, characterized by zero net magnetization and momentum-dependent spin splitting, have recently garnered significant attention due to their potential applications in a variety of fields. Here, we propose a symmetry-engineering strategy to unlock altermagnetism in two dimensional (2D) antiferromagnetic systems via surface adsorption of atoms or molecules. By employing spin group theory, we systematically demonstrate that selectively breaking symmetry operations, specifically those protecting spin degeneracy in momentum space, enables the emergence of nonrelativistic spin-split electronic states. Meanwhile, preserving rotation or mirror symmetries connecting opposite sublattices ensures zero net magnetization. Through a comprehensive classification of all symmetry operations across 80 layer groups, we identify 63 antiferromagnetic spin point groups (SPGs) describing 2D materials and further isolate 15 groups that can host altermagnetic characteristics through surface adsorption. Exemplified with monolayer antiferromagnetic VPS_3 and MnPSe_3, we show that oxygen adsorption on VPS_3 and NH_3 adsorption on MnPSe_3 selectively disrupt PT symmetry while retaining the [C2||m] symmetry. This engineered symmetry reduction induces pronounced spin splitting in their band structures without spin-orbit coupling, as confirmed by first-principles calculations. Furthermore, adsorption energy analysis and thermal stability phase diagrams under varying coverage regimes reveal optimal configurations for experimental feasibility. Our work establishes a universal symmetry-engineering framework to expand the family of altermagnetic materials, offering a versatile pathway to tailor spin-split functionalities in two-dimensional antiferromagnets for advanced quantum applications.

cond-mat.mes-hall↗

arXiv2025

Controllable Antiferromagnetic-Ferromagnetic phase transition in monolayer MnPSe3 via atomic adsorption of Li, O, and F

The engineering of magnetic order and electronic states in two-dimensional (2D) materials is pivotal for advanced spintronic technologies. Despite their potential, the scarcity of intrinsic 2D ferromagnets remains a critical challenge. Here, we employ density functional theory with Hubbard-U corrections to systematically investigate adsorbate-driven magnetic transitions in monolayer MnPSe3. While pristine MnPSe3 exhibits antiferromagnetic (AFM) ordering with a semiconducting gap, Li, O, and F adatom adsorption induces an AFM-to-ferromagnetic (AFM-FM) phase transition across large coverage ranges. Our calculations reveal enhanced thermodynamic stability at elevated coverages, with full-coverage configurations (Li0.5MnPSe3, MnPSe3O0.5, MnPSe3F0.5) favored energetically. Hybrid functional (HSE06) calculations show that F adsorption drives a semiconductor-to-half-metal transition, whereas Li and O adsorption preserves semiconductivity. Moreover, Li adsorption induces a valley splitting of 20.3 meV at the K1 and K2 points in the band structure of the monolayer MnPSe3. Magnetic anisotropy analysis reveals adsorbate-dependent easy-axis reorientation: Li (electron doping) switches the easy-axis from in-plane to out-of-plane, while O/F (hole doping) stabilizes in-plane easy-axis, consistent with carrier-density-modulation simulations. Crucially, carrier doping results indicate that once the electron doping concentration reaches critical concentration, the magnetic easy axis of monolayer MnPSe3 transitions from in-plane to out-of-plane. This work establishes atomic adsorption as a robust strategy for tailoring 2D magnetism, resolving discrepancies through rigorous treatment of exchange-correlation effects and configurational diversity.

cond-mat.mes-hall↗

arXiv2025

Multi-component altermagnet: A general approach to generating multi-component structures with two-dimensional altermagnetism

Altermagnetism, as an unconventional antiferromagnetism, exhibits collinear-compensated magnetic order in real space and spin-splitting band structure in reciprocal space. In this work, we propose a general approach to generating multi-component structures with two-dimensional altermagnetism, based on symmetry analysis. Specifically, by analyzing the space group of the crystal structures and their subgroups, we systematically categorize equivalent atomic positions and arrange them into orbits based on symmetry operations. Chemical elements are then allowed to occupy all atomic positions on these orbits, generating candidate structures with specific symmetries. We present a general technique for generating collinear-compensated magnetic order, characterized by the symmetrical interconnection between opposite-spin sublattices, and employ first-principles calculations to determine magnetic ground states of multi-component materials. This approach integrates symmetry analysis with the screening of altermagnetic configurations to evaluate the likelihood of candidates possessing altermagnetism. To verify the methodology, we provide examples of previously unreported 2D altermagnets, such as Cr2Si2S3Se3, Fe2P2S3Se3, and V2O2BrI3, and evaluate their dynamical stability by calculating the phonon spectrum. The results demonstrate the feasibility of our approach in generating stable multi-component structures with two-dimensional altermagnetism. Our research has significantly enriched the candidate materials for 2D altermagnet and provided a reference for experimental synthesis.

cond-mat.mtrl-sci↗

arXiv2024

Bilayer stacking A-type altermagnet: A general approach to generating two-dimensional altermagnetism

In this article, we propose a new concept of bilayer stacking A-type altermagnet (BSAA), in which two identical ferromagnetic monolayers are stacked with antiferromagnetic coupling to form a two-dimensional A-type altermagnet. By solving the stacking model, we derive all BSAAs for all layer groups and draw three key conclusions: (1) Only 17 layer groups can realize intrinsic A-type altermagnetism. All 2D A-type altermagnets must belong to these 17 layer groups, which will be helpful to search for 2D A-type altermagnet. (2) It is impossible to connect the two sublattices of BSAA using $S_{3z}$ or $S_{6z}$, a constraint that is also applicable to all 2D altermagnets. (3) $C_{2\alpha}$ is a general stacking operation to generate BSAA for an arbitrary monolayer. Our theory not only can explain the previously reported twisted-bilayer altermagnets, but also can provide more possibilities to generate A-type altermagnets. Our research has significantly broadened the range of candidate materials for 2D altermagnets. Based on conclusion (1), the bilayer NiZrCl$_6$ is predicted to exhibit intrinsic A-type altermagnetism. Additionally, we use twisted-bilayer NiCl$_2$, previously reported in the literature, as the second example of BSAA. Furthermore, utilizing symmetry analysis and first-principles calculation, we scrutinize their spin-momentum locking characteristic to substantiate their altermagnetic properties.

cond-mat.mtrl-sci↗

arXiv2024

Description of two-dimensional altermagnetism: Categorization using spin group theory

Altermagnetism, recently spotlighted in condensed matter physics, presents captivating physical properties and holds promise for spintronics applications. This study delves into the theoretical description and categorization of two-dimensional altermagnetism using spin group theory. Employing spin-group formalism, we establish seven distinct spin layer groups, extending beyond the conventional five spin Laue groups, to describe two-dimensional altermagnetism. Utilizing these findings, we classify previously reported two-dimensional altermagnets and identify novel materials exhibiting altermagnetism. Specifically, monolayer MnTeMoO$_6$ and VP$_2$H$_8$(NO$_4$)$_2$ are predicted to be two-dimensional altermagnets. Furthermore, we scrutinize their spin-momentum locking characteristics through symmetry analysis and density functional theory calculations, substantiating their altermagnetic properties.

cond-mat.mtrl-sci↗