Materials with a kagome lattice host exotic quantum phenomena driven by the interplay between band topology, spin-orbit coupling, magnetism, and electronic correlations. While the magnetism of kagome materials has been widely investigated, their unconventional superconductivity (SC) remains largely unexplored due to the limited availability of suitable materials. Here, we report evidence of unconventional SC in the ScIr 2 - x Si x family by combining muon-spin spectroscopy measurements with band-structure calculations. The parent ScIr 2 undergoes a structural phase transition from a high- T cubic- to a low- T rhombohedral phase, while the Ir kagome layer remains, albeit slightly, distorted. Although the structural transition is suppressed by Si substitution, the superconducting pairing of ScIr 2 - x Si x remains well described by a two-gap model. Since at least one of the gaps exhibits nodes, this indicates an unconventional SC. Its unconventional nature can be explained by the distinct flat bands occurring near the Fermi level, leading to strong electronic correlations in the ScIr 2 - x Si x family. Moreover, the low- T phase of ScIr 2 exhibits an Ir chiral chain; therefore, it can be classified as a topological chiral crystal. Overall, the unusual properties of the ScIr 2 - x Si x family make it an interesting, albeit rare, system for studying the interplay between unconventional SC, flat bands, and chirality.

For ultrafast magnetization switching devices, critical slowing down in conventional ferromagnets near their Curie temperature constitutes a key challenge that must be overcome. In contrast to this typical behavior, we observe an anomalous acceleration of demagnetization in CaRuO_3/SrTiO_3 superlattices, a moderately correlated weak itinerant ferromagnet. The demagnetization rate increases with rising temperature, pump fluence, and applied magnetic field. To explain these anomalous phenomena, we develop a phenomenological model integrating the three-temperature model with self-consistent renormalization theory. Because the intrinsic gradient magnetism of the superlattice suppresses the typical divergence of specific heat, the conventional thermodynamic bottleneck is bypassed. Our model reveals that this decoupling enables the ultrafast dynamics to be predominantly governed by the spin-fluctuation-driven enhancement of the electron-spin scattering vertex. Our work demonstrates how spatial inhomogeneity can decouple macroscopic thermodynamic singularities from microscopic scattering processes, offering a new paradigm for manipulating ultrafast spin dynamics in correlated quantum materials. The pronounced sensitivity of the demagnetization rate to external parameters further suggests the potential for designing highly tunable ultrafast spintronic devices that leverage enhanced fluctuations near the magnetic instability.

Moiré semiconductors built on angle-aligned transition metal dichalcogenide (TMD) heterobilayers provide a physical realization of the Kondo lattice model, in which one TMD layer is prepared in a Mott insulating state supporting a lattice of local magnetic moments and the other layer in a metallic state supporting itinerant carriers. The artificial Kondo lattice enables the exploration of exotic states of matter near a continuously tunable Kondo breakdown. Here we report the emergence of a symmetry-broken Chern insulator at a moiré hole filling factor 4/3 in angle-aligned MoTe2/WSe2 moiré bilayers, which realize a chiral Kondo lattice. The symmetry-broken Chern insulator, which exhibits integer quantized Hall conductance at a fractional moiré filling, breaks the translational symmetry of the lattice spontaneously; it also appears only near a magnetic field-induced Kondo breakdown in the mixed-valence regime of the material. We further demonstrate that the magnetic field required to induce the Kondo breakdown and to stabilize the symmetry-broken Chern insulator is twist angle dependent. The results present new opportunities for exploring the subtle interplay between topology and Kondo interactions in moiré semiconductors.

Helically twisted multilayers offer access to moiré physics beyond the single-superlattice paradigm, yet their correlated and topological transport properties remain largely unexplored in semiconductor moiré materials. Here we report magnetotransport measurements of helical trilayer WSe2, in which two coupled moiré patterns relax into a supermoiré landscape composed of inequivalent local topological domains with distinct electronic structures and unequal spatial areas. By electrostatic tuning, we identify a trilayer-hybridized regime where interactions and real-space reconstruction combine to generate a plethora of magnetic and topological states absent in the twisted bilayers. At moiré filling factor ν = -1, we observe a ferromagnetic insulating state that is robust against magnetic field and accompanied by a non-quantized anomalous Hall response -4 kOhms. This behaviour is consistent with a time-reversal-symmetry-breaking supermoiré Chern mosaic, in which the Hall response arises from the non-cancelling contributions of local domains with opposite Chern character arranged by the relaxed structure. Under strong magnetic fields, a symmetry-broken Chern insulating state (C = 1) emerges near ν = -2/3, displaying a much larger positive Hall response together with strongly enhanced longitudinal resistance, suggestive of field-reconstructed topological minibands and domain-boundary scattering. These results establish relaxed supermoiré semiconductor trilayers as a platform for spatially organized magnetism and topology beyond the bilayer limit.

Increasing the number of internal components in a quantum many-body system can host collective orders inaccessible to simpler settings. Quantum Hall bilayers provide a canonical realization of interlayer exciton condensation, yet extending such coherence across three independently addressable electronic fluids has remained elusive. Here we report evidence for three-component interlayer coherent exciton condensation in triple-layer graphene system. Using Rydberg excitons in an adjacent WSe2 monolayer as a layer-sensitive optical probe, we resolve interaction-induced incompressibility at zeroth-Landau-level crossings for all three pairwise layer combinations, establishing top-middle, middle-bottom and top-bottom exciton condensate channels within the same device. Independent control of displacement field and interlayer bias continuously tunes these pairwise states towards a regime where Landau levels from all three layers approach simultaneous degeneracy. At their convergence, incompressibility persists while the exciton energy and spectral weight evolve smoothly between the pairwise limits, suggesting coherent participation of all three layers in a single three-component state. More broadly, the ability to independently control layer potentials and engineer interlayer interactions establishes multilayer graphene as a programmable synthetic dimension for exploring higher-component quantum Hall order and simulating strongly correlated quantum matter.

Abstract Twisted trilayer TMD moiré materials, featuring double moiré patterns and an additional layer degree of freedom, are expected to provide a versatile platform that can generate novel topological physics and correlated emergent states. Here, we systematically investigate the electronic properties of $3.89^{\circ}$ alternating twisted trilayer $\mathrm{W}\mathrm{Se}_2$ by employing ab-initio methods based on machine learning combined with the TAPW. Our calculations reveal an overlap between the first and second moiré bands without a global gap opening. Furthermore, interlayer sliding and an external electric field can modulate interlayer hybridization, thereby tuning the symmetries and quantum geometry of the system. Such interlayer sliding not only drives a valley Chern number transition from $|C|=1$ to $C=0$, but also induces a polarization of the quantum geometry, thereby suggesting a possible route to explore the nonlinear Hall effect.

We investigate lattice relaxation and band structures of helical and alternating twisted trilayer WSe_2 and MoTe_2 using machine-learning force fields and large-scale ab initio calculations. Interference between the two bilayer moiré lattices generates a supermoiré lattice that, upon relaxation, reconstructs into a few dominant domain types with locally commensurate bilayer moiré lattices. Because the systems lack C_2z symmetry, domains otherwise related by this symmetry become energetically and topologically distinct, unlike in twisted trilayer graphene. Band structure calculations show that the topmost valence bands originate from the K (K') valleys and carry domain-dependent valley Chern numbers. The resulting supermoiré lattice hosts a mosaic of topologically inequivalent domains, offering a platform for exploring correlated and topological physics.

Bistability-two distinct stable states under identical parameters-is not only a fundamental physical concept but also of importance in practical applications. While plasmon-polaritonic bistability representing history-dependent stable states within plasmonic systems has been theoretically predicted, it has yet to be demonstrated experimentally due to challenges in realizing suitable nonlinearity at feasible electric-field strengths. Here, we report the experimental observation of electrically driven plasmon-polaritonic bistability in graphene/hexagonal-boron-nitride/graphene tunneling transistors, achieved through momentum-conserving resonant tunneling of Dirac electrons. Using a small twist angle between graphene layers, we engineered devices exhibiting both electronic and plasmon-polaritonic bistability. This bistable plasmonic behavior can be precisely tuned through load resistance and electrostatic gating. Our findings open new pathways for exploring nonlinear optical and electronic phenomena in van der Waals heterostructures and mark a significant advance in nanoplasmonics, with potential applications in optical memory, sensing, and optoelectronic switching.

Recently identified altermagnets exhibit a distinctive dual-space nature: they possess spin-split electronic bands akin to ferromagnets in momentum space while maintaining the fully compensated magnetization of antiferromagnets in real space. This inherent duality, originating from the same crystal symmetry, gives rise to various intriguing physical phenomena unique to altermagnets. Consequently, a robust and efficient experimental signature capable of revealing this dual character is critically needed. The magneto-optical Kerr and Voigt effects, given their high sensitivity to ferromagnetism and antiferromagnetism, respectively, are ideally suited to probe this duality. Here, using time-resolved pump-probe magneto-optical measurements, we report the coexistence of pronounced Kerr and Voigt effects in the altermagnet MnTe. Combining the magnetization measurement and first-principles calculations, we demonstrate that the Kerr effect originates from the intrinsic Berry curvature of altermagnetism distribution in momentum space, while the Voigt effect arises from an anisotropic permittivity induced by the in-plane Néel order in real space, directly revealing the dual-space nature of altermagnets. Furthermore, the transient Kerr signal exhibits faster relaxation dynamics than the transient Voigt signal, underscoring their distinct origins in Berry curvature and Néel order, respectively. These findings establish transient magneto-optical responses as distinctive fingerprints of altermagnetism and position altermagnets as promising platforms for manipulating magneto-optical phenomena in ultrafast spin optoelectronics.

The stacking configuration of two-dimensional materials critically governs their optical and electronic responses. Monolayer transition-metal dichalcogenides (TMDC) lack inversion symmetry and exhibit exciton-enhanced second-harmonic generation (SHG). In TMDC bilayers, 60° (0°) stacking is conventionally expected to suppress (enhance) SHG owing to destructive (constructive) interference of the layer-resolved nonlinear polarizations. Here, we report an unconventional destructive SHG interference in nearly 0°-stacked (AA-stacked) MoTe2/WSe2 heterobilayers using two independent probes: atomic-resolution imaging and stacking-sensitive exciton hybridization measurements. Supported by ab initio GW and Bethe-Salpeter equation calculations, we show that distinct two-photon resonances associated with the WSe2 C exciton and the MoTe2 D exciton generate a nearly π phase difference (Δϕ) in their second-order nonlinear susceptibilities χ^(2), leading to the anomalous destructive interference. We further demonstrate that in small-angle twisted MoTe2/WSe2, the SHG polarization state is governed by the interplay between twist angle α and phase difference Δϕ, and can be mapped onto trajectories on the Poincaré sphere. At excitation energies satisfying Δϕ + 3α = 180°, the SHG output becomes nearly circularly polarized (ellipticity 0.91) and undergoes an abrupt 90° azimuthal rotation, corresponding to a geometric polarization singularity in the parameter space. Our findings open new routes for exciton-resonance engineered nonlinear photonics and stacking-resolved optical functionality in moiré materials.

Exotic quantum phenomena are often found to occur in spin systems that exhibit low-dimensional magnetism. By combining nuclear magnetic resonance, neutron scattering, and muon-spin spectroscopy (μSR) techniques, we report a rare instance of strongly frustrated two-dimensional (2D) magnetism in a three-dimensional (3D) hexagonal perovskite. Here, Ba_2La_2MnTe_2O_12, a triangular-lattice magnet, is shown to undergo a magnetic transition at T_N≈ 4.4 K, below which the manganese moments form a 120^∘ AFM order within the ab-plane, while staying disordered along the c-axis. This exotic ground state, which exhibits ideal 2D magnetism, is highly consistent with the persistently strong spin fluctuations and the large internal field distributions revealed by zero-field μSR. Further, the 2D magnetism also leads to a significant frustration, much larger than that of most known magnetically-ordered frustrated systems. Our work on Ba_2La_2MnTe_2O_12 not only challenges the interpretations of magnetic order in other 3D hexagonal perovskites, but it also provides insight into how the dimensionality affects the exotic magnetic states.

The cubic Cu3Au-type X Pt3 family (X = V, Cr, and Mn) is a topological semimetal characterized by anticrossing gapped nodal lines near the Fermi level, which give rise to significant Berry curvatures and thus the to the anomalous Hall effect (AHE). Among the three members, CrPt3 has been experimentally verified to exhibit a large anomalous Hall conductivity (AHC), while its counterparts MnPt3 and VPt3 remain largely unexplored. Here, a series of MnPt3 thin films with varying thicknesses (20-70 nm) was epitaxially grown on the MgO substrates using magnetron sputtering and was systematically investigated by magnetization, electrical resistivity, and Hall resistivity measurements. MnPt3 films undergo a ferromagnetic transition at a Curie temperature TC, which increases as the film thickness increases, reaching similar to 344 K for the 70-nm-thick film. All the anomalous Hall transport properties of MnPt3 films, including the resistivity, conductivity, and angle, exhibit a strong correlation with their magnetic properties. The scaling analysis suggests that the intrinsic Berry-curvature mechanism dominates the observed AHE, while the extrinsic contributions are much smaller. The intrinsic AHC increases as the film thickness increases, while the extrinsic AHC is thickness independent. Such an enhanced intrinsic AHC in the MnPt3 films is most likely attributed to the strain effect, implying that it serves as an effective method to tune the electronic band topology in the X Pt3 topological semimetal.

The alpha-GeTe is a typical ferroelectric Rashba semiconductor (FERSC) that has attracted a lot of attention in spintronics. The Fe/alpha-GeTe grown on Si substrates has anisotropic Gilbert damping. However, the effect of Al2O3, as another common substrate, remains unknown when alpha-GeTe is grown on it. Here, we fabricated alpha-GeTe thin films using Al2O3 substrates. The alpha-GeTe directly grown on Al2O3 exhibits an in-plane polycrystalline structure. A Bi2Te3 buffer layer can make the alpha-GeTe exhibit a single-crystal feature. The anisotropic Gilbert damping of FM layers is present in Fe/alpha-GeTe/Bi2Te3/Al2O3 and vanished in Fe/alpha-GeTe/Al2O3. Our finding illustrates that alpha-GeTe growth on Al2O3 with a Bi2Te3 buffer layer can serve as a suitable platform for anisotropic research. Our work paves the way for the application of the Al2O3-based alpha-GeTe thin films in anisotropic electronics.

Electron tunneling is a central transport mechanism in nanoscale devices. The advent of two-dimensional (2D) van der Waals materials has greatly expanded the ability to explore unconventional tunneling phenomena in heterostructures. Conventionally, studies in these systems have focused on tunneling between a pair of electrodes separated by a barrier. Here we report a previously overlooked tunneling pathway in which electrons traverse both the barrier and the electrode to reach semiconductor layers placed outside the junction. We identify this mechanism through the observation of prominent conductance peaks in tunneling transport measurements. Combined transport and optical spectroscopy reveal that the conductance peaks are of different origin than the accompanying electroluminescence. While conductance peaks originate from electrons tunneling through the graphene-hBN-graphene barrier into empty states of the semiconductor, electroluminescence peaks originate from recombination of excitons excited via energy transfer. Our work uncovers the impact of the electronic environment adjacent to tunnel junctions and serves as a pristine probe of the material’s electronic properties. It also establishes a versatile platform for multidimensional investigations of tunneling processes, enabling new designs for on-chip optoelectronic applications.

van der Waals (vdW) forces in two-dimensional materials allow for versatile control over interlayer coupling, enabling the exploration of novel emergent quantum states and device functionalities. Here, using microreflectance spectroscopy in a diamond anvil cell, we demonstrate dynamic pressure tuning of layer-hybridized excitons in dual-gated trilayer WSe2 devices up to 6.6 GPa. Pressure-controlled interlayer coupling manifests as enhanced energy-level anticrossings and oscillator strength redistribution between the intralayer and interlayer excitons. We observe an 11% reduction in the interlayer exciton dipole moment, while the coupling strength triples (from ∼10 to >30 meV), following a near-linear scaling of 3.5 ± 0.2 meV/GPa. Spectral density simulations resolve four distinct components of hybridized excitons, i.e., intralayer ground/excited and interlayer ground/excited states, with their relative weights transitioning from one component dominant to strongly mixed at higher pressures. Our findings highlight the potential for controlling excitonic properties and engineering optoelectronic devices through interlayer compression.

In this work, InSnZnO (ITZO) thin films with different structural phases were obtained via Al-induced microstructure regularization (AIMR) method. The thin-film transistor (TFT) with amorphous front-channel and polycrystalline back-channel exhibits remarkable field-effect mobility (μFE) boosted to 115.2 cm2/Vs which is about twice that of the TFT with fully-crystallized channel. It is found that the partially-crystallized ITZO shows a denser microstructure with less oxygen vacancies (VO) in the front-channel region compared to the fully-crystallized one. Other electrical properties as well as the negative-bias-stress stability are also improved. TCAD simulations were performed to investigate the defect states in the channel, providing supportive evidence for the experimental results. Keeping the amorphous state and promoting its microstructure ordering to the utmost is a promising strategy to achieve high-mobility oxide TFTs.

Developing bulk nonlinear optical (NLO) crystals that simultaneously combine outstanding optical performance with excellent crystal growth capability remains a major challenge. Here, we introduce an intrinsic coordination asymmetry strategy that exploits highly polarizable tetrahedral Hg-S coordination and conformationally flexible ligands to amplify local structural distortions within discrete homoanionic modules. Guided by this concept, Cc-(NH4)2Hg(SCN)4 (Cc-AHT) and its C2/c polymorph were synthesized. Structural and theoretical investigations reveal that the flexible (SCN)ligands propagate distortions originating in the [HgS4] core throughout the [Hg(SCN)4]2-module, establishing an atomic-shell distortion amplification model that quantitatively traces the evolution of local coordination asymmetry. Cc-AHT exhibits a giant second-harmonic generation response (14 × KH2PO4 and 1.2 × KTiOPO4 at 1064 nm), a band gap of 3.25 eV, and large birefringence (Δn = 0.341 at 1064 nm), while centimeter-sized single crystals can be readily grown under mild conditions. This work establishes intrinsic coordination asymmetry and its atomic-shell amplification as a chemically guided strategy for designing high-performance homoanionic NLO materials and provides a general framework for understanding how local structural distortions propagate through coordination modules containing conformationally flexible ligands.