Bin Cui

The spin Hall and orbital Hall effects are fundamental mechanisms for generating transverse spin and orbital currents. However, their intrinsic entanglement via spin-orbit coupling (SOC) has made the generation of pure spin or orbital Hall current a long-standing challenge. Here, we demonstrate a strategy not only to generate but also to reversibly switch between spin and orbital Hall currents within a single material. Combining first-principles calculations with tight-binding modeling, we show that spin-orbital-valley locking, together with external-field-controlled topological band inversion, enables a reversible crossover of Hall transport between spin- and orbital-dominated regimes, even yielding a dominant spin Hall response in weak-SOC systems. Our Letter provides a direct route toward disentangling mixed spin-orbital transport and establishes a versatile platform for the independent control and probing of spin and orbital degrees of freedom.

Due to the high cost of Pt catalysts, designing low-cost and high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) has become a key challenge in the development of renewable energy technology.

Photodetectors with high photoresponsivity are crucial in a wide range of emerging fields. Here, we report the realization of photodetectors based on co-assembled composite membranes consisting of copper phthalocyanine (CuPc) molecules and graphene oxide (GO) sheets, showing a photoresponsivity as high as ~ 10⁷ A/W under 3 nW illumination and a moderate external pressure (~1 atm) in the visible range. We attribute the high photoresponsivity to the pressure-induced optimization of the atomic-level heterojunctions between photoactive CuPc molecules and adjacent GO sheets in the photodetector, which enhances the electronic coupling at the heterojunction for charge transport. The photodetectors show good flexibility for electronic skin applications, enabling simultaneous contact sensing and non-contact perception under ambient illumination down to dim moonlight. The developed strategy provides a promising perspective for fabricating next-generation photoelectric conversion devices with potential applications spanning intelligent sensing, aerospace technologies, and defence-related photonic platforms.

Crystalline porous organic frameworks, including covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs), provide geometrically tunable platforms for exotic electronic phenomena. Through symmetry analysis and first-principles calculations, we demonstrate that two-dimensional organic breathing kagome (BK) COF and HOF exhibit pronounced orbital Hall effect (OHE), nonlinear Hall effect (NHE), and nonequilibrium orbital magnetization (NEOM) driven by breathing-induced inversion-symmetry breaking (ISB). Due to the negligible spin-orbit coupling (SOC) in organic materials, these responses originate purely from geometric modulation, enabling reversible control of the orbital angular momentum and Berry curvature and thus switchable OHE, NHE, and NEOM. Notably, OHE persists across gaps induced by both Haldane and ISB effects, while NHE and NEOM are exclusively observed in the ISB regime and maintain breathing-tunable characteristics. Our findings identify organic BK lattices as an ideal SOC-free geometry-controllable platform for realizing and manipulating OHE and NHE.

Nonlinear optical (NLO) responses are vital for lasers, sensing, and quantum technologies. In two-dimensional systems, many-body excitonic effects can profoundly modify NLO responses, giving rise to novel exciton-mediated NLO phenomena. However, our understanding of these effects in real materials remains limited, particularly regarding controllable manipulation of NLO responses via excitons. Here, we report strong excitonic second-harmonic generation (SHG) in an experimentally synthesized, ground-state-stable Janus monolayer, RhSeCl. Combining density functional theory and many-body perturbation theory, we reveal that its giant SHG arises not only from intrinsic symmetry breaking but also crucially from an exciton-assisted double resonance mechanism. In bilayers, distinct stacking configurations enable giant SHG modulation, accompanied by a switch in the dominant contribution from intralayer to interlayer excitons. Vertical electric fields further enhance tunability through precise control of hybridization between interlayer and intralayer excitons. Our finding establishes Janus materials as a promising excitonic NLO platform, enabling the systematic design of nonlinear quantum light sources through controlled exciton engineering.

Bulk photovoltaic effect (BPVE) is a novel nonlinear-optical (NLO) effect for the development of advanced optoelectronic devices. Here, we report a new type of BPVE, chirality-dependent orbital BPVE (orbit-BPVE), in a one-dimensional (1D) helical system, whose orbital-polarized photocurrent is solely determined by the chirality. This orbit-BPVE is contributed by the chirality-dependent orbital angular momentum (OAM), and the chirality-locked spin-BPVE is a secondary effect arising from the orbit-BPVE, mediated by spin-orbit coupling (SOC). The minimal-model calculations further demonstrate that the robust orbit-BPVE persists even at small screw angles and varying SOC strength, and the orbit-BPVE remains more pronounced than spin-BPVE in a wide range of SOC strengths. These results establish 1D chiral systems as a universal platform for orbitronic device engineering, where geometric chirality directly encodes optoelectronic functionality.

Ultrahigh photoresponsivity is crucial in a wide range of emerging fields. Here, we report a photodetector with ultrahigh photoresponsivity that outperforms all the current state-of-the-art photodetectors under illumination powers from 3 nW to 10 mW. Remarkably, photoresponsivity as high as ~ 10⁷ A/W is achieved under 3 nW illumination, surpassing the previously reported values by more than one order of magnitude. The key to the high photoresponsivity lies in the optimization on the atomic-level heterojunctions between photoactive copper phthalocyanine molecules and adjacent graphene oxide sheets in the photodetector, which greatly enhances the electronic coupling at the heterojunction for charge transport. This photodetector has good flexibility, enabling simultaneous contact sensing and non-contact perception serving as a novel electronic skin under ambient illumination down to dim moonlight. The developed strategy provides a new perspective for fabricating next-generation photoelectric conversion devices with potential applications spanning intelligent sensing, aerospace technologies, and defense-related photonic platforms.