Jing Zhang

This review focuses on the advance in flexible and stretchable electrochemical sensors (FSECSs) for biological monitoring. The fabrication of FSECSs with emphasis on stretchable electrodes and some key strategies for improving their performance is summarized. Then, their applications in exploring the chemical information from different biological entities, including epidermis, tissues both in vitro and in vivo, and cells, are highlighted.

Abstract

The rise of flexible and stretchable electronics has revolutionized biosensor techniques for probing biological systems. Particularly, flexible and stretchable electrochemical sensors (FSECSs) enable the in situ quantification of numerous biochemical molecules in different biological entities owing to their exceptional sensitivity, fast response, and easy miniaturization. Over the past decade, the fabrication and application of FSECSs have significantly progressed. This review highlights key developments in electrode fabrication and FSECSs functionalization. It delves into the electrochemical sensing of various biomarkers, including metabolites, electrolytes, signaling molecules, and neurotransmitters from biological systems, encompassing the outer epidermis, tissues/organs in vitro and in vivo, and living cells. Finally, considering electrode preparation and biological applications, current challenges and future opportunities for FSECSs are discussed.

Herein, a high underlayer coverage of sub-millimeter bilayer graphene single crystal is achieved successfully, by modifying the gas flow streamline in the circumfluence chemical vapor deposition, which is attributed to the promotion of carbon sources depositing and absorbing on the copper surface under the vertical streamline.

The growth of large-scale bilayer graphene (bi-graphene) is significantly important for graphene-based device fabrications. Chemical vapor deposition is usually used for the synthesis of high-quality and large-scale thin films including various monolayers and bilayers. However, a major challenge for bi-graphene growth is the so-called limited underlayer coverage, i.e., the faster growth of the top layer than the underlayer. Herein, using the circumfluence chemical vapor deposition, it is demonstrated that the underlayer growth can be greatly enhanced via optimizing the streamline, and high-quality AB-stacking sub-millimeter bi-graphene with underlayer coverage over 93% is achieved successfully. Raman spectroscopy and selected area electron diffraction confirm the high crystalline quality and uniformity of the as-grown bilayers. The as-fabricated field-effect transistor using the bi-graphene as the channel layer exhibits typical semiconductor transfer characteristics and a nonzero bandgap which is required for device applications. It is suggested that the optimized streamline design largely allows a reduction of difference in the edge growth kinetics between the top and bottom layers. Thus, in this work, a promising technical route is presented for the growth of large-scale bi-graphene with high underlayer coverage, beneficial for the development of functional graphene devices.

Inspired by the magic stairs, an innovative and complementary integration of light-field and structured-light depth mapping and imaging system using a size of 1.2 × 1.2 mm² meta-lens array to measure the depth over a 30 cm range is shown. This compact, lightweight, low power consumption system can be used for autonomous systems in all light levels conditions.

Abstract

The optical illusion affects depth-sensing due to the limited and specific light-field information acquired by single-lens imaging. The incomplete depth information or visual deception would cause cognitive errors. To resolve this problem, an intelligent and compact depth-sensing meta-device that is miniaturized, integrated, and applicable for diverse scenes in all light levels is demonstrated. The compact and multifunction stereo vision system adopts an array with 3600 achromatic meta-lenses and a size of 1.2 × 1.2 mm² to measure the depth over a 30 cm range with deep-learning support. The meta-lens array can act as multiple imaging lenses to collect light field information. It can also work with a light source as an active optical device to project a structured light. The meta-lens array can serve as the core functional component of a light-field imaging system under bright conditions or a structured-light projection system in the dark. The depth information in both ways can be analyzed and extracted by the convolutional neural network. This work provides a new avenue for the applications such as autonomous driving, machine vision, human–computer interaction, augmented reality, biometric identification, etc.

Metasurface-enhanced infrared spectroscopy has emerged as a highly sensitive tool for detecting and monitoring the constituents of molecular systems. This review showcases a variety of metaresonator sensors based on different resonance principles, geometries, and materials. The unique functionalities they offer for molecular studies, including dielectrophoresis-based cell trapping and sensing, as well as AI-augmented monitoring of biomolecular systems are discussed.

Abstract

Infrared spectroscopy provides unique information on the composition and dynamics of biochemical systems by resolving the characteristic absorption fingerprints of their constituent molecules. Based on this inherent chemical specificity and the capability for label-free, noninvasive, and real-time detection, infrared spectroscopy approaches have unlocked a plethora of breakthrough applications for fields ranging from environmental monitoring and defense to chemical analysis and medical diagnostics. Nanophotonics has played a crucial role for pushing the sensitivity limits of traditional far-field spectroscopy by using resonant nanostructures to focus the incident light into nanoscale hot-spots of the electromagnetic field, greatly enhancing light–matter interaction. Metasurfaces composed of regular arrangements of such resonators further increase the design space for tailoring this nanoscale light control both spectrally and spatially, which has established them as an invaluable toolkit for surface-enhanced spectroscopy. Starting from the fundamental concepts of metasurface-enhanced infrared spectroscopy, a broad palette of resonator geometries, materials, and arrangements for realizing highly sensitive metadevices is showcased, with a special focus on emerging systems such as phononic and 2D van der Waals materials, and integration with waveguides for lab-on-a-chip devices. Furthermore, advanced sensor functionalities of metasurface-based infrared spectroscopy, including multiresonance, tunability, dielectrophoresis, live cell sensing, and machine-learning-aided analysis are highlighted.

By constructing a planar field emission (FE)-type photodetector of monolayer WS₂ with microtips, high photoresponsivity and fast response time can be achieved at the same time. This novel planar FE device may shed new light on the fabrication of high-performance 2D material-based photodetectors.

Abstract

Monolayer tungsten disulfide (ML WS₂) is believed as an ideal photosensitive material due to its small direct bandgap, large exciton/trion binding energy, high carrier mobility, and considerable quantum conversion efficiency. Compared with other photosensitive devices, planar field emission (FE)-type photodetectors with a full-plane structure should simultaneously have rapider switching speed and lower power consumption. In this work, ML WS₂ microtips are fabricated by electron beam lithography (EBL) way and used to construct a planar FE-type photodetector. By optimization design, ML WS₂ with three microtips can exhibit the maximum current density as high as  52 A cm⁻² (@300 V µm⁻¹), and the largest photoresponsivity is up to 6.8 × 10⁵ A W⁻¹ under green light irradiation, superior to that of many other ML transition metal dichalcogenide (TMDC) detectors. More interestingly, ML WS₂ devices with microtips can effectively solve the contradictory problem between large photoresponsivity and rapid switching speed. The excellent photoresponse performances of ML WS₂ with microtips should be attributed to their high carrier mobility, sharp emission edge, ultrahigh quantum yield, and unique planar FE device structure. Our research may shed new light on exploring the fabrication technology and photosensitive mechanism of two dimensional (2D) material-based planar FE photodetectors.

Nature Communications, Published online: 25 August 2023; doi:10.1038/s41467-023-40765-1

Recently, rich condensed matter physics has emerged from the interplay between band topology and magnetic order. Here, the authors characterize the magnetic Weyl semimetal CeAlGe and find evidence for the role of Weyl fermions in stabilizing the magnetic order above the local transition temperature.

Confining atomically thin Pt nanoclusters on 2D δ-MoN by virtue of strong metal-support interaction (SMSI) enables an energetically favorable multi-active site mechanism, resulting in outstanding pH-universal hydrogen evolution reaction activity. The SMSI-enhanced 2D ultrathin structure features seamless electronic and mass transports with minimal resistances and robust structural stability that render a durable catalytic performance under harsh operating conditions.

Abstract

Engineering precious metals’ sub-nanometer cluster on 2D earth-abundant supports provides a promising approach for the development of high-efficient electrocatalysts in pursuit of green hydrogen. Herein, a novel solid phase deposition approach is demonstrated for the homogenous confinement of atomically thin Pt nanoclusters on 2D delta-MoN as a viable catalyst for pH-universal hydrogen evolution reaction. Notably, the optimized material (MoN-5% Pt) exhibits excellent catalytic performance as evidenced by low overpotentials required, excellent mass activity exceeding 20 A mg_Pt ⁻¹ at 100 mV overpotential, and outstanding stability with negligible activity degradation. The enhanced performance is attributed to (1) novel nanostructure, constituting atomically thin Pt nanoclusters confined on 2D δ-MoN substrate, thus rendering high atomic utilization and seamless surface mass transfer, and (2) influence of strong metal-support interaction that effectively limits structural deformation and performance degradation. Theoretical simulations reveal that the strong metal-support interaction induces substantial charge redistribution across the heterointerface, initiating an energy-favorable multi-active site microkinetics in which Pt atoms with an optimal hydrogen adsorption energy making way for enhanced H2 evolution, while Mo atoms situated at the heterointerface enhance water absorption/dissociation steps, enriching the catalytic surface with adsorbed hydrogen atoms.

A quasi-2D electron gas of charge carriers is realized in a bulk 3D oxide perovskite. Furthermore, these carriers have magnetically controllable topological spin textures and are of a single orbital character, making it an ideal platform for spintronic devices.

Abstract

2D phases of matter have become a new paradigm in condensed matter physics, bringing in an abundance of novel quantum phenomena with promising device applications. However, realizing such quantum phases has its own challenges, stimulating research into non-traditional methods to create them. One such attempt is presented here, where the intrinsic crystal anisotropy in a “fractional” perovskite, Eu _x TaO₃ (x = 1/3 − 1/2), leads to the formation of stacked layers of quasi-2D electron gases, despite being a 3D bulk system. These carriers possess topologically non-trivial spin textures, indirectly controlled by an external magnetic field via proximity effect, making it an ideal system for spintronics, for which several possible applications are proposed. An anomalous Hall effect with a non-monotonic dependence on carrier density is shown to exist, signifying a shift in band topology with carrier doping. Furthermore, quantum oscillations in charge conductivity and oscillating thermoelectric properties are examined and proposed as routes to experimentally demonstrate the quasi-2D behavior.

Nature Materials, Published online: 24 August 2023; doi:10.1038/s41563-023-01589-y

This Perspective provides an overview on the emergent field of colloidal robotics, discussing recent developments on colloidal and micrometre-sized particles that can perform functions such as sensing, communication, computation and motion.

A radical-free, Diels–Alder-based photopatterning platform is presented which enables the spatially defined modification of protein-based hydrogels with dienophile-bearing biomolecules. By utilizing commercially available maleimide-functionalized streptavidin and biotinylated species of interest, a robust mix-and-match platform is demonstrated. Through the immobilization of biotinylated growth factors, the use of these engineered substrates to program cell behaviors is highlighted.

Abstract

Strategies that mimic the spatial complexity of natural tissues can provide cellular scaffolds to probe fundamental questions in cell biology and offer new materials for regenerative medicine. Here, the authors demonstrate a light-guided patterning platform that uses natural engineered extracellular matrix (ECM) proteins as a substrate to program cellular behaviors. A photocaged diene which undergoes Diels–Alder-based click chemistry upon uncaging with 365 nm light is utilized. By interfacing with commercially available maleimide dienophiles, patterning of common ECM proteins (collagen, fibronectin Matrigel, laminin) with readily purchased functional small molecules and growth factors is achieved. Finally, the use of this platform to spatially control ERK activity and migration in mammalian cells is highlighted, demonstrating programmable cell behavior through patterned chemical modification of natural ECM.

For the first time, strong photorefractive effects are demonstrated of 2D metal-halide ferroelectric, involving with the light-induced variation of electric polarization. This work will promote the study of photorefractive ferroelectrics and shed light on optical controlling of physical properties in electric-ordered materials.

Abstract

Photorefractive effect of ferroelectrics refers to the light-induced change of refractive index, which is an optical controlling avenue in holographic storage and image processing. For most ferroelectrics, however, the small photorefractive effect (10⁻⁵–10⁻⁴) hinders their practical application and it is urgent to exploit new photorefractive system. Here, for the first time, strong photorefractive effects are achieved in a 2D metal-halide ferroelectric, [CH₃(CH₂)₃NH₃]₂(CH₃NH₃)Pb₂Cl₇ (1), showing large spontaneous polarization (≈4.1 µC cm⁻²) and wide optical bandgap (≈3.20 eV). Notably, under light irradiation, 1 enables a large variation of refractive indices up to ≈ 1× 10⁻³, being one order higher than the existing materials and comparable to the state-of-the-art inorganic ferroelectrics. This intriguing photorefractive behavior involves with the sharp variation of polarization caused by photo-pyroelectricity. As the first report of 2D metal-halide photorefractive ferroelectric, this work sheds light on optical controlling of physical properties in electric-ordered materials.

Nature, Published online: 23 August 2023; doi:10.1038/d41586-023-02569-7

As the resources required by artificial intelligence increase unsustainably, an analog design provides an energy-efficient alternative to digital computer chips — and one that is ideally suited to neural-network computations.

Nature, Published online: 23 August 2023; doi:10.1038/d41586-023-02655-w

Ordinary ballpoint pens loaded with conductive inks ‘write’ LEDs onto textiles, packaging and more.

A heavy transition metal oxide CaRuO₃ with strong spin-orbit coupling can be driven into a fully ferromagnetic state (∼0.8 μ_B/Ru) by the magnetic proximity effect. The anomalous Hall conductivity and Hall angle are one to two orders of magnitude larger than those of the typical 3d ferromagnetic oxides. It is worth emphasizing that the magnetic anisotropy of (LaMnO₃/CaRuO₃) superlattices is eightfold symmetric.

Abstract

Ferromagnetic materials with a strong spin-orbit coupling (SOC) have attracted much attention in recent years because of their exotic properties and potential applications in energy-efficient spintronics. However, such materials are scarce in nature. Here, a proximity-induced paramagnetic to ferromagnetic transition for the heavy transition metal oxide CaRuO₃ in (001)-(LaMnO₃/CaRuO₃) superlattices is reported. Anomalous Hall effect is observed in the temperature range up to 180 K. Maximal anomalous Hall conductivity and anomalous Hall angle are as large as ∼15 Ω⁻¹ cm⁻¹ and ∼0.93%, respectively, by one to two orders of magnitude larger than those of the typical 3d ferromagnetic oxides such as La_0.67Sr_0.33MnO₃. Density functional theory calculations indicate the existence of avoid band crossings in the electronic band structure of the ferromagnetic CRO layer, which enhances Berry curvature thus strong anomalous Hall effects. Further evidences from polarized neutron reflectometry show that the CaRuO₃ layers are in a fully ferromagnetic state (∼0.8 μ_B/Ru), in sharp contrast to the proximity-induced canted antiferromagnetic state in 5d oxides SrIrO₃ and CaIrO₃ (∼0.1 μ_B/Ir). More than that, the magnetic anisotropy of the (001)-(LaMnO₃/CaRuO₃) superlattices is eightfold symmetric, showing potential applications in the technology of multistate data storage.

A facile one-step process to create ordered polymer networks via cooperative photo-alignment and -polymerization is presented. The noncontact method appears independent of both matrix and substrate composition, which will enable the fabrication of next-generation “smart” plastics for medicine and information security.

Abstract

Spatial control over molecular order in polymeric systems will enable advancements in healthcare and photonics, from soft actuators to data storage and encryption. Liquid crystalline (LC) materials are attractive for their intrinsic combination of long-range anisotropy and fluidity that enables alignment. Photoalignment represents an attractive noncontact ordering mechanism. However, contemporary hurdles preventing widespread implementation of photoalignment include the use of high-intensity light sources, restrictions to thin films (<1 µm) and specific substrates, multistep LC syntheses, and costly processing. Herein, an interplay between photo-polymerization and -alignment with commercially relevant LCs is reported. Systematic, in situ monitoring of optical anisotropy using a custom microscopy setup provides unique mechanistic insight and facilitates optimization. The optimized process occurs rapidly (<10 min) from an isotropic state with a one-step exposure to low-intensity blue linearly polarized light. As a result, substrate-independent photoalignment of thick (≈6–38 µm), optically transparent LC networks is demonstrated, along with a wide LC-matrix scope that includes thiol-containing elastomers. Furthermore, photopatterning provides excellent fidelity (<5 µm) and access to complex images with multiangle optical anisotropy. This user-friendly process will facilitate production of “smart” (stimuli-responsive) plastics for improved human health and information security.

Stretchable high-resolution multicolor synesthesia display, which can generate synchronized sound and light as input/output sources, is fabricated by transfer-printing. With its inherent stretchability, the synesthesia display can stably operate under both static and dynamic deformations. In addition, the potential application as an input device is showcased through user-interactive visual–acoustic encryption and the creation of a multiplex quick response code.

Abstract

Multifunctional displays, which have various functions in single-device systems without external circuits, are actively investigated as future human–machine interfaces owing to performability of unprecedented functions in compact design. However, their application is limited to visualize the mechanical/electrical signals in light. Herein, stretchable high-resolution multicolor synesthesia display, which can generate synchronized sound and light as input/output sources, is presented by transfer-printing. Transfer-printed emissive composite leads to display with enhanced optical performance and fine sound pressure level. Owing to inherent stretchability of the device, the synesthesia display can stably operate under static and dynamic deformation without distortion in sound relative to the input waveform. User-interactive synesthesia displays are demonstrated for visual−acoustic encryption, which facilitate advanced encryption, as well as multiplex quick response code that bridges multiple domains with a single device. This approach provides new directions for multifunctional displays, with potential applications in reinforced authentication.

Recent progress in synthesis methods, surface modification, T ₁-weighted magnetic resonance imaging (MRI) strategies, and MRI-guided cancer therapy utilizing emerging exceedingly small magnetic iron oxide nanoparticles (ES-MIONs) is summarized.

Abstract

Magnetic iron oxide nanoparticles (MIONs) based T ₂-weighted magnetic resonance imaging (MRI) contrast agents (CAs) are liver-specific with good biocompatibility, but have been withdrawn from the market and replaced with Eovist (Gd-EOB-DTPA) due to their inherent limitations (e.g., susceptibility to artifacts, high magnetic moment, dark signals, long processing time of T ₂ imaging, and long waiting time for patients after administration). Without the disadvantages of Gd-chelates and MIONs, the recently emerging exceedingly small MIONs (ES-MIONs) (<5 nm) are promising T ₁ CAs for MRI. However, there are rare review articles focusing on ES-MIONs for T ₁-weighted MRI. Herein, the recent progress of ES-MIONs, including synthesis methods (the current basic synthesis methods and improved methods), surface modifications (artificial polymers, natural polymers, zwitterions, and functional protein), T ₁-MRI visual strategies (structural remodeling, reversible self-assemblies, metal ions doped, T ₁/T ₂ dual imaging modes, and PET/MRI strategy), and imaging-guided cancer therapy (chemotherapy, gene therapy, ferroptosis therapy, photothermal therapy, photodymatic therapy, radiotherapy, immuotherapy, sonodynamic therapy, and multimode therapy), is summarized. The detailed description of synthesis methods and applications of ES-MIONs in this review is anticipated to attract extensive interest from researchers in different fields and promote their participation in the establishment of ES-MIONs based nanoplatforms for tumor theranostics.

Enhancement of the second harmonic generation (SHG) from monolayer MoS2 is achieved by embedding it in a double resonant distributed Bragg reflector microcavity, with one resonance at second harmonic of the other. This creates a twofold pathway to the increased enhancement of SHG by enhancing the interaction at the excitation wavelength as well as the SHG itself.

Abstract

A characteristic property of monolayered transition metal dichalcogenides is their strong nonlinear response. While they display a high conversion efficiency per atomic layer, due to their low thickness, the absolute value of their nonlinear response remains low. Here enhancement of the second harmonic generation (SHG) of monolayer MoS₂ through the design, fabrication, and characterization of a monolithic microcavity, which aims to be double resonant at a fundamental wavelength of λ = 800 nm as well as its second harmonic, is demonstrated. The MoS₂ monolayers are embedded in such a cavity, with the aim to simultaneously enhance the light-matter interaction at the excitation wavelength and the SHG from the monolayers. A resonance enhancement for the SHG process is achieved through the cavity.

This review highlightsrecent progress in the field of nanoelectronics utilizing metal-insulatortransition (MIT) behaviors in Mott insulators. It covers a wide range oftopics, from the microscopic interactions in condensed matter systems to themacroscopic device functionalities by various external stimuli. This review servesas an overview and a comprehensive understanding of the design of next-generation MIT-based nanoelectronics.

Abstract

Metal–insulator transition (MIT) coupled with an ultrafast, significant, and reversible resistive change in Mott insulators has attracted tremendous interest for investigation into next-generation electronic and optoelectronic devices, as well as a fundamental understanding of condensed matter systems. Although the mechanism of MIT in Mott insulators is still controversial, great efforts have been made to understand and modulate MIT behavior for various electronic and optoelectronic applications. In this review, recent progress in the field of nanoelectronics utilizing MIT is highlighted. A brief introduction to the physics of MIT and its underlying mechanisms is begun. After discussing the MIT behaviors of various Mott insulators, recent advances in the design and fabrication of nanoelectronics devices based on MIT, including memories, gas sensors, photodetectors, logic circuits, and artificial neural networks are described. Finally, an outlook on the development and future applications of nanoelectronics utilizing MIT is provided. This review can serve as an overview and a comprehensive understanding of the design of MIT-based nanoelectronics for future electronic and optoelectronic devices.

The wafer-scale synthesis and device processing of 2D materials (2DMs) for integrated circuit applications are reviewed, emphasizing the criticality of process integration towards practical manufacturing. The feasibility of transitioning from laboratory research to industrial-scale utilization is also discussed, while identifying potential integration issues that need to be addressed.

Abstract

The atomically thin nature and exceptional electrical properties of 2D materials (2DMs) have garnered significant interest in circuit applications. Researchers have developed circuits based on wafer-level 2DM fabrication and monolithic integration in the laboratory. Numerous studies have been conducted on discrete device processes; however, circuit manufacturing is a multifaceted and methodical engineering process that demands seamless integration of multiple procedures. Notably, the optimization of crucial processes holds paramount significance in achieving expected results. This review presents the existing research on process integration of 2DM devices and circuit applications. The selection of suitable 2DMs for circuit applications is outlined, considering their excellent theoretical properties and feasible high-quality growth processes. Drawing on highly mature semiconductor manufacturing process, while incorporating customized key processes, 2DM devices have the potential to strongly compete with, and even outperform, the conventional devices. Finally, the recent circuit applications of 2DMs are also discussed in detail. 2DM integrated circuits (2DM ICs) are now being practically applied in advanced manufacturing, transitioning from laboratory development to fabrication plant deployment. The implementation of underlying 2DM IC fabrication provides effective and unique solutions for More Moore, More than Moore, and Beyond CMOS technology routes.

2D Antiferromagnetic Semiconductors

Distinct from the established spin-flop type metamagnetism, in article number 2300964, Yi Zheng, Jinbo Yang, Yunhao Lu, Chenqiang Hua, and co-workers report the unconventional spin-lattice interlocked metamagnetism in a frustrated an der Waals (vdW) magnet. These unconventional metamagnetic transitions produce a unique field-tunable ferrimagnetic (FiM) phase with the magnetization axis freely rotated by magnetic field within an easy plane.

Topological insulator 2D Bi (110) nanosheets are obtained by a novel reductive electrochemical exfoliation method with the highest yield ever reported. These nanosheets are stabilized through exfoliation in a reductive environment and further modification with polymer ionic liquids, and then utilized for fabricating flexible acoustic sensors with ultrahigh sensitivity and the ability of information transfer.

Abstract

Topological insulators (TIs) are characterized by a full insulating gap in the bulk and gapless edge or surface states, which have attracted tremendous attention. 2D Bi (110), as a typical TI, is of particular interest due to its low symmetry structure and topologically protected and spin-momentum-locked Dirac surface states. However, the material's potential applications are hindered by difficulties in fabrication, due to its strong semi-metallic bonding and poor stability. In this study, a novel electrochemical intercalation method for the fabrication of ultrathin Bi (110) nanosheets with the highest yield ever reported is presented. These nanosheets are stabilized through cathodic exfoliation in a reductive environment and further modification with polymer ionic liquids. The versatility of these nanosheets is demonstrated by fabricating flexible acoustic sensors with ultrahigh sensitivity. These sensors can even detect sounds as quiet as 45 dB. Furthermore, these sensors are utilized for acoustic-to-electric energy conversion and information transfer. This work offers a promising approach for scalable fabrication and preservation of ultrathin 2D TI Bi (110) nanosheets and paves the way for their integration into smart devices.

Nature Physics, Published online: 17 August 2023; doi:10.1038/s41567-023-02174-5

Previous work has suggested that at very low temperatures TbInO3 hosts an unconventional quantum ground state. Terahertz time-domain spectroscopy measurements of its excitations show that related exotic effects can persist to room temperature.

Nature Electronics, Published online: 17 August 2023; doi:10.1038/s41928-023-01013-y

It is shown that 1,024 organic light-emitting diodes can be densely integrated with silicon complementary metal–oxide–semiconductor control circuitry to create neural probes that can selectively activate neurons with millisecond-level timing.

Unconventional, nodal superconductors appear in many strongly correlated systems, including cuprate superconductors and heavy-fermion systems. However, nodal monolayer van der Waals superconductors have not yet been reported. The scanning tunneling microscopy experiments on 1H-TaS₂ demonstrate nodal superconductivity in a van der Waals monolayer, providing a building block for van der Waals heterostructures exploiting unconventional superconducting states.

Abstract

Unconventional superconductors represent one of the fundamental directions in modern quantum materials research. In particular, nodal superconductors are known to appear naturally in strongly correlated systems, including cuprate superconductors and heavy-fermion systems. Van der Waals materials hosting superconducting states are well known, yet nodal monolayer van der Waals superconductors have remained elusive. Here, using low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) experiments, it is shown that pristine monolayer 1H-TaS₂ realizes a nodal superconducting state. Non-magnetic disorder drives the nodal superconducting state to a conventional gapped s-wave state. Furthermore, many-body excitations emerge close to the gap edge, signalling a potential unconventional pairing mechanism. The results demonstrate the emergence of nodal superconductivity in a van der Waals monolayer, providing a building block for van der Waals heterostructures exploiting unconventional superconducting states.

Topological Hall Effect

In article number 2302984, Xuefeng Wang, Hongxin Yang, Binghui Ge, and co-workers report the large-area, high-quality epitaxy of ferromagnetic Cr₅Te₆ single-crystalline thin films with the colossal topological Hall effect (THE), which is attributed to the field-induced noncoplanar spin textures. The THE can be maintained near the room temperature, which could find promising device applications in chiral spintronics.

Nature Nanotechnology, Published online: 17 August 2023; doi:10.1038/s41565-023-01492-2

A giant spin Hall effect with long spin diffusion length and coexisting with ferromagnetism is observed in AB-stacked MoTe2/WSe2 moiré hetero-bilayers.

Nature Physics, Published online: 17 August 2023; doi:10.1038/s41567-023-02174-5

Previous work has suggested that at very low temperatures TbInO3 hosts an unconventional quantum ground state. Terahertz time-domain spectroscopy measurements of its excitations show that related exotic effects can persist to room temperature.

Nature Materials, Published online: 14 August 2023; doi:10.1038/s41563-023-01596-z

Controlling the periodicity of synthesized moiré materials is vital to harness their unique physics. Here the authors realize the van der Waals epitaxy of tunable moiré heterostructures and reveal the epitaxial science governing their formation.

Anti-ambipolar heterojunctions hold promising potential for next-generation integrated circuit chips and telecommunication technologies, enabled by their high data processing efficiency, lower power consumption, and simplified circuit design. This review summarizes the historical and recent advances in anti-ambipolar heterojunctions, highlighting their significance in materials, devices, circuits, and broad scale research.

Abstract

Anti-ambipolar heterojunctions are vital in constructing high-frequency oscillators, fast switches, and multivalued logic (MVL) devices, which hold promising potential for next-generation integrated circuit chips and telecommunication technologies. Thanks to the strategic material design and device integration, anti-ambipolar heterojunctions have demonstrated unparalleled device and circuit performance that surpasses other semiconducting material systems. This review aims to provide a comprehensive summary of the achievements in the field of anti-ambipolar heterojunctions. First, the fundamental operating mechanisms of anti-ambipolar devices are discussed. After that, potential materials used in anti-ambipolar devices are discussed with particular attention to 2D-based, 1D-based, and organic-based heterojunctions. Next, the primary device applications employing anti-ambipolar heterojunctions, including anti-ambipolar transistors (AATs), photodetectors, frequency doublers, and synaptic devices, are summarized. Furthermore, alongside the advancements in individual devices, the practical integration of these devices at the circuit level, including topics such as MVL circuits, complex logic gates, and spiking neuron circuits, is also discussed. Lastly, the present key challenges and future research directions concerning anti-ambipolar heterojunctions and their applications are also emphasized.