Xuezhi Ma

Altermagnetism is a compensated magnetic order in which spin polarization alternates between symmetry-related momenta despite zero net magnetization. Recently, an altermagnetic photonic crystal was demonstrated by mapping electron spin onto light spin, while still relying on gyromagnetic materials and magnetic bias. Hence, it is rather elusive to extend the altermagnetism concept to optical frequencies. Here we realize reconfigurable magnet-free alterspin photonics in an all-dielectric photonic crystal across 740–800 nm. The in-plane square lattice fixes the four-period angular form of the alterspin texture, while an extrinsic out-of-plane dielectric perturbation controls its sign and amplitude. A liquid droplet enables writing, erasing, and reversing the alterspin texture. We further establish a criterion to evaluate the alterspin order and quantify the measured texture. Our results provide a route toward visible-to-near-infrared alterspin photonic systems that are magnet-free and externally reconfigurable.

Van der Waals (vdW) ferroelectrics are emerging nonlinear photonic materials that combine large second-order susceptibility χ(2) with heterostructure compatibility, offering an attractive route toward miniaturized spontaneous parametric down-conversion (SPDC) sources. Practical vdW SPDC, however, remains constrained by low brightness and poor stability in air under continuous irradiation, where ambient exposure and pump-induced heating cause material degradation. Here we demonstrate a bright, air-stable SPDC source based on ferroelectric NbOI2 enabled by graphene encapsulation. Graphene provides robust environmental protection and suppresses pump-induced degradation by enhancing heat dissipation. We report an absolute photon-pair generation rate of 258 Hz and a normalized brightness of 19 900 Hz mW–1 mm–1. Leveraging this stabilized platform, we further generate polarization-entangled photon pairs from graphene-encapsulated 90°-twisted bilayer NbOI2, with 94% fidelity to a maximally entangled Bell state. These results establish graphene-encapsulated NbOI2 as a practical vdW ferroelectric SPDC platform for integrated quantum photonic sources.

Grasping objects such as handles, mice, and phones plays a central role in human-machine interaction, yet the contact surfaces of the hand, despite their exquisite tactile sensitivity, are rarely exploited as channels for information transfer. Here, we introduce transdermal all-directional targeting (TADT), a static-contact interface design strategy that converts passive grip surfaces into active tactile displays, allowing users to grasp stably while receiving spatially and temporally evolving information on the fingertips. TADT enhances sub-actuator-pitch energy delivery by integrating a microtextured skin-coupling interface with phase-controlled vibrotactile actuation, thereby generating steerable three-dimensional tactile foci beneath the skin, enabling >200-hertz vibration and sub-actuator-pitch spatial super-resolution. Psychophysical experiments show that TADT lowers detection thresholds by 30% and reduces power consumption by 80% compared with designs without TADT. Using static grip alone, users reliably identified six directional cues and completed nonvisual indoor navigation and virtual reality interaction tasks, demonstrating a compact, energy-efficient modality for expressive tactile communication.

Predictive optical modelling of van der Waals (vdW) heterostructures is critical for meta-optics, near-field photonics and quantum technologies. At their buried interfaces, charge transfer and spatially extended screening challenge local descriptions based on layer-by-layer stacking of fixed permittivity tensors. However, such nonlocal corrections have been established mainly for plasmonic systems at ångström-nanometre scales and are often assumed negligible on optical-wavelength scales. Here we challenge this view by uncovering a mesoscopic nonlocal screening regime, extending up to ~140 nm, at buried charge-transfer interfaces in transition-metal dichalcogenide/ α -molybdenum trioxide (TMDC/ α -MoO ₃ ) phonon-polaritonic heterostructures. Using phonon polaritons as an ultrasensitive probe, we quantify charge transfer from polariton-wavelength shifts and find a thickness-independent saturated response as α -MoO ₃ is thinned. Rather than merely complicating optical modelling, this nonlocal saturation turns a design-level correction into an opportunity by yielding a transferable cross-material metric. Across more than 120 devices, this metric scales linearly with the work-function difference between the TMDC and α -MoO ₃ . We further identify a lattice-mismatch-set energy threshold for charge transfer, revising Anderson-type band alignment for vdW interfaces.

This review analyses the state-of-the-art transfer methods of 2D materials, evaluates their strengths and limitations, and highlights emerging trends like reconfigurable transfer, all-transfer strategies and broad applications in diverse fields.

Integrated photodetectors are vital for their high speed, sensitivity, and low power consumption, with photocurrent driven by the photovoltaic and photothermoelectric (PTE) effects. At the nanoscale, these mechanisms overlap, complicating their separate evaluation. We introduce a 3D photocurrent nanoimaging technique to map these effects in a MoS ₂ -Au Schottky photodiode, revealing a PTE-dominated region extending hundreds of nanometers from the electrode edge, enabled by weak electrostatic forces in two-dimensional materials. Unexpectedly, adding high–thermal conductivity hexagonal boron nitride enhances the PTE response by laterally redirecting heat, aligning thermal gradients with Seebeck coefficient variations, and boosting local conductance. This technique advances optoelectronic applications and deepens insights into light-matter interactions in low-dimensional systems, offering a powerful tool for designing efficient nanoscale photodetectors.

Anisotropic optical crystals can exhibit a hyperbolic response within the Reststrahlen band (RB) and support directional polaritonic propagations when interacting with light. Most of the reported low-symmetry optical crystals showcase the evolution from hyperbolic to elliptic dispersion topologies, largely owing to their adjacent RBs being either overlapped or separated. Here, we report an exceptional Reststrahlen point (ERP) in rare-earth oxyorthosilicate Y₂SiO₅, at which two neighboring RBs almost kiss each other. Consequently, we observe the direct hyperbolic-to-hyperbolic topological transition: the hyperbolic branches close and reopen along with the rotating transverse axis (TA). At such ERP, the TA merges to the direction orthogonal to its proximate phonon mode, mainly due to the interplay between these two non-orthogonal phonon modes. We also find that even with the existence of only one single RB, the TA can rotate in-plane. Our findings are prevalent in isostructural rare-earth oxyorthosilicates, such as Lu₂SiO₅. The universally underlying physics of ERP and its corresponding special class of rare-earth oxyorthosilicates may offer playgrounds for continuously tuning phonon polariton propagation direction, and broadband controlling light dispersion of polaritonic nanodevices.

As basic optical elements, waveplates with anisotropic electromagnetic responses are imperative for manipulating light polarization. Conventional waveplates are manufactured from bulk crystals (e.g., quartz and calcite) through a series of precision cutting and grinding steps, which typically result in large size, low yield, and high cost. In this study, a bottom‐up method is used to grow ferrocene crystals with large anisotropy to demonstrate self‐assembled ultrathin true zero‐order waveplates without additional machining processing, which is particularly suited for nanophotonic integration. The van der Waals ferrocene crystals exhibit high birefringence (Δn (experiment) = 0.149 ± 0.002 at 636 nm), low dichroism Δκ (experiment) = −0.0007 at 636 nm), and a potentially broad operating range (550 nm to 20 µm) as suggested by Density Functional Theory (DFT) calculations. In addition, the grown waveplate's highest and the lowest principal axes (n₁ and n₃, respectively) are in the a–c plane, where the fast axis is along one natural edge of the ferrocene crystal, rendering them readily usable. The as‐grown, wavelength‐scale‐thick waveplate allows the development of further miniaturized systems via tandem integration.