Yalong Jiao

In conventional two-dimensional (2D) transition-metal dichalcogenides (TMDCs), intrinsic mirror symmetry forbids out-of-plane dipoles and suppresses symmetry-enabled properties. Janus TMDCs provide a direct route to mirror-symmetry breaking; however, their chemically inequivalent surfaces often introduce local strain imbalance and structural distortions. Designing symmetry-broken TMDC architectures that combine high structural stability with retained symmetry-derived functionality is therefore crucial. Here, we introduce complementary chalcogen ordering as a strategy for balanced symmetry breaking in 2D MSSe monolayers (M: transition metals). In this architecture, S and Se atoms are arranged into ordered, complementary patterns across the two chalcogen sublayers, thereby decoupling mirror-symmetry breaking from the severe surface and bonding imbalances characteristic of Janus monolayers. By scanning all transition metals, we find that nearly 79% of the proposed structures are energetically more favorable than their Janus counterparts. Five highly stable monolayers are identified, spanning nonmagnetic, ferromagnetic, and antiferromagnetic ground states, as well as metallic and semiconducting electronic structures. These materials exhibit diverse functionalities, including high Curie temperatures, phototunable spin textures, ferroelasticity, and enhanced thermoelectric performance. This work establishes complementary chalcogen ordering as a general design principle for stabilizing symmetry-broken 2D TMDCs and unlocking symmetry-enabled multifunctionality beyond the Janus paradigm.

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.

The electrochemical nitrogen reduction reaction (NRR) offers a sustainable approach to ammonia (NH ₃ ) synthesis under mild conditions. To achieve scalable NH ₃ production, discovering high‐performance catalysts for the efficient NRR is crucial. For this purpose, the activity mechanisms of functional group‐modified carborin/graphene‐supported single‐atom catalysts were systematically investigated using the grand‐canonical fixed‐potential method, which simulates operando constant‐potential conditions. Among 144 candidates screened, Cr@NO ₂ ‐carborin/graphene and Cr@CHO‐carborin/graphene are identified as the most promising NRR catalysts, with low limiting potentials of −0.220 V for the ^* N ₂ → ^* N ₂ H step and −0.245 V for the ^* NH→ ^* NH ₂ step, respectively. Furthermore, interpretable machine learning models revealed that the shift in potential of zero charge, induced by intermediate adsorption, serves as the key voltage‐responsive descriptor governing charge transfer patterns and influencing the N ₂ activation. These findings establish a paradigm shift from static electronic descriptors to dynamic interfacial property engineering, offering a universal framework for designing electrocatalysts for multi‐electron reactions like NRR.

Achieving ultrafast room-temperature magnetism control in two-dimensional (2D) altermagnetic (AM) materials is a major challenge in spintronics. In this study, we identify Cr₂MoS₄ as a promising material to overcome these limitations, combining exceptional stability, robust altermagnetism, and laser-tunable electronic and magnetic properties. Cr₂MoS₄ features an in-plane magnetic easy axis with a magnetic anisotropy energy of 0.24 meV/Cr and a high critical temperature of 400 K, well-above room temperature. Upon laser pulse irradiation, Cr₂MoS₄ undergoes rapid electron and phonon temperature rises, resulting in ultrafast demagnetization within ∼200 fs─comparable to antiferromagnetic Dirac semimetals. Transient thermal effects further induce structural distortions, breaking mirror symmetry and generating valley polarization in Cr₂MoS₄. Beyond single-pulse excitation, we apply a double-pulse with adjustable time delays (200-1000 fs), enabling precise modulation of spin dynamics. Tuning the delay allows for control over demagnetization times, amplification of demagnetization effects, and even the reversal of the recovery process into repeated demagnetization. These findings establish Cr₂MoS₄ as an excellent platform for spintronic applications and offer new insights into ultrafast optical control of AM spin dynamics.

Current strategies for stabilizing 2D borophene sheets and compensating for boron's electron deficiency primarily rely on transition metals, many of which are heavy and costly, thereby limiting their practical applications. In contrast, the use of light‐metal elements to stabilize borophene has remained largely unexplored. This work demonstrates that the light‐metal beryllium (Be) can effectively stabilize 2D boron sheets. Through swarm‐intelligence structural searches combined with first‐principles calculations, three stable monolayers of beryllium tetraboride (BeB ₄ )—the α‐, β‐, and γ‐phases—are predicted. The α‐BeB ₄ phase is metallic, while β‐ and γ‐BeB ₄ are indirect semiconductors with bandgaps of 0.39 and 1.65 eV, respectively. Notably, biaxial strain can reversibly tune β‐BeB ₄ between semiconducting and metallic states. Furthermore, γ‐BeB ₄ exhibits a high visible‐light absorption coefficient (3.80 × 10 ⁵ cm ^{− 1} ) and an out‐of‐plane negative Poisson's ratio, indicating auxetic behavior. Remarkably, α‐BeB ₄ demonstrates a near‐zero Gibbs free energy for hydrogen adsorption, suggesting excellent catalytic activity for the hydrogen evolution reaction. These unique properties position BeB ₄ monolayers as promising, lightweight, and cost‐effective candidates for next‐generation energy conversion and optoelectronic applications.

Superatoms, stable atomic clusters acting as building blocks for new materials, offer unique opportunities due to their rich properties and potential for 2D material assembly. While their similarities to atoms have been extensively studied, their internal degrees of freedom (IDOFs) remain underexplored. Concurrently, compensated antiferromagnets (AFMs) with spin-split band structures have emerged as a promising class of materials for spintronics, yet their experimental realization, particularly in two dimensions, is limited. We propose a novel strategy to engineer spin-split AFMs by using superatoms with IDOFs. We demonstrate how superatom IDOFs can manipulate the system symmetry to induce spin splitting in AFM states. First-principles calculations on Mo-decorated carborophene, built from closo-carborane superatoms, show that distinct IDOFs (electric-dipole-like and nematic) dictate the 2D crystal's symmetry and spin-splitting patterns. This highlights the unique role of superatom IDOFs, absent in ordinary atoms, and establishes a new paradigm for designing advanced spintronic and quantum materials.

Highly stable transition metal monoxide sheets are predicted to exhibit Dirac fermions and demonstrate high efficiency for photocatalytic CO ₂ reduction.

Superatoms, stable atomic clusters acting as building blocks for new materials, offer unique opportunities due to their rich properties and potential for 2D material assembly. While extensive research has focused on their similarities to ordinary atoms, the role of their internal degrees of freedom (IDOF) remains largely unexplored. Concurrently, compensated antiferromagnets (AFMs) with intrinsic spin-split band structures have emerged as a promising class of materials for spintronics, yet their experimental realization, particularly in two dimensions, is limited. Here, we bridge these two fields by proposing a novel strategy to achieve spin-split AFMs using superatoms with IDOFs. We establish our core concept using a simple model, demonstrating how superatom IDOFs can be leveraged to engineer system symmetry and induce spin splitting in AFM states. We concretely illustrate this strategy by first-principles calculations on a Mo-decorated carborophene sheets, constructed from closo-carborane superatoms. We show that the distinct IDOFs of carborane isomers (electric-dipole-like and nematic) are critical in determining the symmetry of the resulting 2D superatomic crystal and, consequently, the spin splitting pattern of its AFM states. Our findings underscore the profound significance of superatom IDOFs-a feature absent in ordinary atoms-and introduce a new paradigm for engineering spin splitting in AFM lattices. This work opens novel avenues for the design of advanced spintronic and quantum materials based on superatoms.