Origin of Nonlinear Circular Photocurrent in 2D Semiconductor MoS_{2}.

Nonlinear photogalvanic effects in two-dimensional materials, particularly the nonlinear circular photocurrents (NCPs) that belong to the helicity-dependent spin photocurrents, have sparked enormous research interest. Although notable progress has been witnessed, the underling origin of NCPs remains elusive. Here, we present systematic photocurrent characteristics, symmetry analysis and theoretical calculations to uncover the physical origin of NCPs in MoS_{2}, a prototypical 2D semiconductor.

A tunable entangled photon-pair source based on a Van der Waals insulator.

Scalable quantum photonic devices drive the development of compact sources of entangled photons, which are pivotal for quantum communication, computing, and cryptography. In this work, we present entangled photon pair generation in rhombohedral boron nitride (r-BN), leveraging its unique optical and structural properties. Unlike conventional hexagonal boron nitride, which suffers from reduced nonlinear response due to centrosymmetric structure in even-layered stacks, r-BN features interlayer ABC stacking and maintains robust in-plane inversion symmetry.

Layer-by-Layer Connection for Large Area Single Crystal Boron Nitride Multilayer Films.

Boron nitride (BN) is today considered one of the most promising materials for many novel applications including bright single photon emission, deep UV optoelectronics, small-sized solid-state neutron detectors, high-performance two-dimensional materials, etc. Recently, AA' stacking a few layers (2-5 layers) of BN films and ABC stacking multilayer (2.2-12 nm) BN films have been successfully synthesized, respectively.

Sandwich-Structured ZnO/MXene Heterojunction for Sensitive and Stable Room-Temperature Ammonia Sensing.

2D metal carbides/nitrides (MXenes) have attracted considerable interests in NH sensing due to their high electrical conductivity and abundant terminal groups. However, the strong interlayer interactions between MXene nanosheets result in challenges related to sensor recovery and rapid response decay in MXene-based sensors. Here, A one-step hydrothermal strategy is developed that anchors Zn atoms and grows ZnO polycrystals on the Ti vacancies of TiCT layers, forming a sandwich-structured ZnO/TiCT heterojunction.

Transferrable, wet-chemistry-derived high-k amorphous metal oxide dielectrics for two-dimensional electronic devices.

Two-dimensional (2D) materials hold transformative potential for next-generation electronics. The integration of high dielectric constant (k) dielectrics onto 2D semiconductors, while maintaining their pristine properties by low-defect-density interfaces, has proven challenging and become one performance bottleneck of their practical implementation. Here, we report a wet-chemistry-based method to fabricate amorphous, transferable high-k (42.

Ferroelectricity with concomitant Coulomb screening in van der Waals heterostructures.

Interfacial ferroelectricity emerges in non-centrosymmetric heterostructures consisting of non-polar van der Waals (vdW) layers. Ferroelectricity with concomitant Coulomb screening can switch topological currents or superconductivity and simulate synaptic response. So far, it has only been realized in bilayer graphene moiré superlattices, posing stringent requirements to constituent materials and twist angles.

Anomalous photovoltaics in Janus MoSSe monolayers.

The anomalous photovoltaic effect (APE) in polar crystals is a promising avenue for overcoming the energy conversion efficiency limits of conventional photoelectric devices utilizing p-n junction architectures. To facilitate effective photocarrier separation and enhance the APE, polar materials need to be thinned down to maximize the depolarization field. Here, we demonstrate Janus MoSSe monolayers (~0.

Nanoscale thickness Octave-spanning coherent supercontinuum light generation.

Coherent broadband light generation has attracted massive attention due to its numerous applications ranging from metrology, sensing, and imaging to communication. In general, spectral broadening is realized via third-order and higher-order nonlinear optical processes (e.g.

Short-Time Preamplification-Assisted One-Pot CRISPR Nucleic Acid Detection Method with Portable Self-Heating Equipment for Point-of-Care Diagnosis.

Infectious diseases, especially respiratory infections, have been significant threats to human health. Therefore, it is essential to develop rapid, portable, and highly sensitive diagnostic methods for their control. Herein, a short-time preamplified, one-pot clustered regularly interspaced short palindromic repeats (CRISPR) nucleic acid detection method (SPOC) is developed by combining the rapid recombinase polymerase amplification (RPA) with CRISPR-Cas12a to reduce the mutual interference and achieve facile and rapid molecular diagnosis.

Sliding ferroelectric memories and synapses based on rhombohedral-stacked bilayer MoS.

Recent advances have uncovered an exotic sliding ferroelectric mechanism, which endows to design atomically thin ferroelectrics from non-ferroelectric parent monolayers. Although notable progress has been witnessed in understanding the fundamental properties, functional devices based on sliding ferroelectrics remain elusive. Here, we demonstrate the rewritable, non-volatile memories at room-temperature with a two-dimensional (2D) sliding ferroelectric semiconductor of rhombohedral-stacked bilayer MoS.

Stacking Engineering toward Giant Second Harmonic Generation in Twisted Graphene Superstructures.

The nonlinear optical response in graphene is finding increasing applications in nanophotonic devices. The activation and enhancement of second harmonic generation (SHG) in graphene, which is generally forbidden in monolayer and AB-stacked bilayer graphene due to their centrosymmetry, is of urgent need for nanophotonic applications. Here, we present a comprehensive study of SHG performance of twisted multilayer graphene structures based on stacking engineering.

3D Crystal Construction by Single-Crystal 2D Material Supercell Multiplying.

2D stacking presents a promising avenue for creating periodic superstructures that unveil novel physical phenomena. While extensive research has focused on lateral 2D material superstructures formed through composition modulation and twisted moiré structures, the exploration of vertical periodicity in 2D material superstructures remains limited. Although weak van der Waals interfaces enable layer-by-layer vertical stacking, traditional methods struggle to control in-plane crystal orientation over large areas, and the vertical dimension is constrained by unscalable, low-throughput processes, preventing the achievement of global order structures.

Growth of Noncentrosymmetric Two-Dimensional Single Crystals.

Among the various two-dimensional (2D) materials, more than 99% of them are noncentrosymmetric. However, since the commonly used substrates are generally centrosymmetric, antiparallel islands are usually inevitable in the growth of noncentrosymmetric 2D materials because of the energetic equivalency of these two kinds of antiparallel islands on centrosymmetric substrates. Therefore, achieving the growth of noncentrosymmetric 2D single crystals has long been a great challenge compared with the centrosymmetric ones like graphene.

β-GaO Nanoribbon with Ultra-High Solar-Blind Ultraviolet Polarization Ratio.

Solar-blind ultraviolet (UV) detection plays a critical role in imaging and communication due to its low-noise background, high signal-to-noise ratio, and strong anti-interference capabilities. Detecting the polarization state of UV light can enhance image information and expand the communication dimension. Although polarization detection is explored in visible and infrared light, and applied in fields such as astrophysics and submarine seismic wave detection, solar-blind UV polarization detection remains largely unreported.

Room-Temperature Two-Dimensional InSe Plasmonic Laser.

Two-dimensional (2D) semiconductors, owing to their strong excitonic emission, are emerging as efficient gain media for constructing the ultimate nanolaser. The further integration of 2D semiconductors with plasmonic devices holds promise for realizing the thinnest laser. However, the implementation of 2D semiconductor plasmonic lasing is severely hindered by the limited cavity feedback and low gain resulting from insufficient plasmon-exciton interactions.

Two-Dimensional Exciton Oriented Diffusion via Periodic Potentials.

Excitonic devices operate based on excitons, which can be excited by photons as well as emitting photons and serve as a medium for photon-carrier conversion. Excitonic devices are expected to combine the advantages of both the high response rate of photonic devices and the high integration of electronic devices simultaneously. However, because of the neutral feature, exciton transport is generally achieved via diffusion rather than using electric fields, and the efficient control of exciton flux directionality has always been difficult.

All-2D-Materials Subthreshold-Free Field-Effect Transistor with Near-Ideal Switching Slope.

The Boltzmann Tyranny, set by thermionic statistics, dictates the lower limit of switching slope (SS) of a MOSFET to be 60 mV/dec, the fundamental barrier for low-dissipative electronics. The large SS leads to nonscalable voltage, significant leakage, and power consumption, particularly at short channels, making transistor scaling an intimidating challenge. In recent decades, an array of steep-slope transistors has been proposed; none is close to an ideal switch with ultimately abrupt switching (SS ∼ 0 mV/dec) between the binary logic states.

Understanding epitaxial growth of two-dimensional materials and their homostructures.

The exceptional physical properties of two-dimensional (2D) van der Waals (vdW) materials have been extensively researched, driving advances in material synthesis. Epitaxial growth, a prominent synthesis strategy, enables the production of large-area, high-quality 2D films compatible with advanced integrated circuits. Typical 2D single crystals, such as graphene, transition metal dichalcogenides and hexagonal boron nitride, have been epitaxially grown at a wafer scale.

Interfacial epitaxy of multilayer rhombohedral transition-metal dichalcogenide single crystals.

Rhombohedral-stacked transition-metal dichalcogenides (3R-TMDs), which are distinct from their hexagonal counterparts, exhibit higher carrier mobility, sliding ferroelectricity, and coherently enhanced nonlinear optical responses. However, surface epitaxial growth of large multilayer 3R-TMD single crystals is difficult. We report an interfacial epitaxy methodology for their growth of several compositions, including molybdenum disulfide (MoS), molybdenum diselenide, tungsten disulfide, tungsten diselenide, niobium disulfide, niobium diselenide, and molybdenum sulfoselenide.