Xingxing Zhang

MXene microstrip patch antennas with ultrahigh‐power radiation in a wide frequency range are fabricated by spray‐coating. The radiation efficiency of a 5.5 µm thick MXene patch antenna reaches 99% at 16.4 GHz, which is about the same as that of a 35 µm thick copper patch antenna. MXene outperforms all other materials evaluated for patch antennas to date.

Abstract

Highly integrated, flexible, and ultrathin wireless communication components are in significant demand due to the explosive growth of portable and wearable electronic devices in the fifth‐generation (5G) network era, but only conventional metals meet the requirements for emerging radio‐frequency (RF) devices so far. Here, it is reported on Ti₃C₂T _x MXene microstrip transmission lines with low‐energy attenuation and patch antennas with high‐power radiation at frequencies from 5.6 to 16.4 GHz. The radiation efficiency of a 5.5 µm thick MXene patch antenna manufactured by spray‐coating from aqueous solution reaches 99% at 16.4 GHz, which is about the same as that of a standard 35 µm thick copper patch antenna at about 15% of its thickness and 7% of the copper weight. MXene outperforms all other materials evaluated for patch antennas to date. Moreover, it is demonstrated that an MXene patch antenna array with integrated feeding circuits on a conformal surface has comparable performance with that of a copper antenna array at 28 GHz, which is a target frequency in practical 5G applications. The versatility of MXene antennas in wide frequency ranges coupled with the flexibility, scalability, and ease of solution processing makes MXene promising for integrated RF components in various flexible electronic devices.

Molybdenum disulfide/rGO vertical heterostructures are demonstrated to possess triple enzyme‐like activities, which are further enhanced through light irradiation. Coupled with the rough surface that contributes excellent capacity for bacterial capture, preeminent antibacterial efficacy against drug‐resistant bacteria is exhibited both in vitro and in vivo by such a defect‐rich adhesive nanozyme, which will blaze a new path for the development of alternative antibiotics.

Abstract

Nanomaterials with intrinsic enzyme‐like activities, namely “nanozymes,” are showing increasing potential as a new type of broad‐spectrum antibiotics. However, their feasibility is still far from satisfactory, due to their low catalytic activity, poor bacterial capturing capacity, and complicated material design. Herein, a facile synthesis of a defect‐rich adhesive molybdenum disulfide (MoS₂)/rGO vertical heterostructure (VHS) through a one‐step microwave‐assisted hydrothermal method is reported. This simple, convenient but effective method for rapid material synthesis enables extremely uniform and well‐dispersed MoS₂/rGO VHS with abundant S and Mo vacancies and rough surface, for a performance approaching the requirements of practical application. It is demonstrated experimentally and theoretically that the as‐prepared MoS₂/rGO VHS possesses defect and irradiation dual‐enhanced triple enzyme‐like activities (oxidase, peroxidase, and catalase) for promoting free‐radical generation, owing to much more active edge sites exposure. Meanwhile, the VHS‐achieved rough surface exhibits excellent capacity for bacterial capture, with elevated reactive oxygen species (ROS) destruction through local topological interactions. As a result, optimized efficacy against drug‐resistant Gram‐negative and Gram‐positive bacteria can be explored by such defect‐rich adhesive nanozymes, demonstrating a simple but powerful way to engineered nanozymes for alternative antibiotics.

The generation of (anti)meron chains from conventional domain walls is directly observed at zero field in 2D ferromagnetic Fe_{5− x} GeTe₂, which closely correlates with the weak van der Waals interaction and temperature‐dependent spin anisotropy transformation. The simultaneous topological Hall effect and the collectively dynamic behavior of the (anti)meron chains under external fields experimentally highlight the theoretical prediction of magnetic‐domain‐wall topology.

Abstract

The promise of topologically vortex‐like magnetic spin textures hinges on the intriguing physical properties and theories in fundamental research and their distinguished roles as high‐efficiency information units in future spintronics. The exploration of such magnetic states with unique spin configurations has never ceased. In this study, the emergence of unconventional (anti)meron chains from a domain wall pair is directly observed at zero field in 2D ferromagnetic Fe_{5− x} GeTe₂, closely correlated with significant enhancement of the in‐plane magnetization and weak van der Waals interactions. The simultaneous appearance of a large topological Hall effect is observed at the same temperature range as that of the abnormal magnetic transition. Moreover, the distinctive features of the (anti)meron chains and their collective dynamic behavior under external fields may provide concrete experimental evidence for the recent theoretical prediction of the magnetic‐domain‐wall topology and endorse a broader range of possibilities for electronics, spintronics, condensed matter physics, etc.

A 2D lateral heterostructure is in situ fabricated. Benefiting from the strong chemical bonding at the heterointerface, a strong internal electric field is generated between two components of the heterostructure, which facilitates photoexcited charge separation and transfer kinetics, and results in improved solar‐energy conversion efficiency.

Abstract

Photocarrier recombination remains a big barrier for the improvement of solar energy conversion efficiency. For 2D materials, construction of heterostructures represents an efficient strategy to promote photoexcited carrier separation via an internal electric field at the heterointerface. However, due to the difficulty in seeking two components with suitable crystal lattice mismatch, most of the current 2D heterostructures are vertical heterostructures and the exploration of 2D lateral heterostructures is scarce and limited. Here, lateral epitaxial heterostructures of BiOCl @ Bi₂O₃ at the atomic level are fabricated via sonicating‐assisted etching of Cl in BiOCl. This unique lateral heterostructure expedites photoexcited charge separation and transportation through the internal electric field induced by chemical bonding at the lateral interface. As a result, the lateral BiOCl @ Bi₂O₃ heterostructure demonstrates superior CO₂ photoreduction properties with a CO yield rate of about 30 µmol g⁻¹ h⁻¹ under visible light illumination. The strategy to fabricate lateral epitaxial heterostructures in this work is expected to provide inspiration for preparing other 2D lateral heterostructures used in optoelectronic devices, energy conversion, and storage fields.

Electronic state transitions in highly crystalline antiferromagnetic CrN films are mediated with strain and reduced dimensionality. Surprisingly, the CrN layer is still highly conductive when its thickness shrinks to 1‐unit‐cell, which is far below the critical thickness of most metallic films. The ability to achieve highly conductive nitride ultrathin films can be used for utilizing their exceptional characteristics.

Abstract

Strain engineering provides the ability to control the ground states and associated phase transition in epitaxial films. However, the systematic study of the intrinsic character and strain dependency in transition‐metal nitrides remains challenging due to the difficulty in fabricating stoichiometric and high‐quality films. Here the observation of an electronic state transition in highly crystalline antiferromagnetic CrN films with strain and reduced dimensionality is reported. By shrinking the film thickness to a critical value of ≈30 unit cells, a profound conductivity reduction accompanied by unexpected volume expansion is observed in CrN films. The electrical conductivity is observed surprisingly when the CrN layer is as thin as a single unit cell thick, which is far below the critical thickness of most metallic films. It is found that the metallicity of an ultrathin CrN film recovers from insulating behavior upon the removal of the as‐grown strain by the fabrication of freestanding nitride films. Both first‐principles calculations and linear dichroism measurements reveal that the strain‐mediated orbital splitting effectively customizes the relatively small bandgap at the Fermi level, leading to an exotic phase transition in CrN. The ability to achieve highly conductive nitride ultrathin films by harnessing strain‐control over competing phases can be used for utilizing their exceptional characteristics.

2D transition metal dichalcogenides have promising properties for future semiconductor technologies. Their integration into functional devices requires cost‐efficient and large‐scale passivation and protection against material deposition. This work introduces ultrathin Ga₂O₃ glass as a new, scalable capping material for monolayer WS₂. It exhibits a novel passivation mechanism and offers extraordinary protection against deposition of dielectric materials, for example, for top‐gating.

Abstract

Atomically thin transition metal dichalcogenide crystals (TMDCs) have extraordinary optical properties that make them attractive for future optoelectronic applications. Integration of TMDCs into practical all‐dielectric heterostructures hinges on the ability to passivate and protect them against necessary fabrication steps on large scales. Despite its limited scalability, encapsulation of TMDCs in hexagonal boron nitride (hBN) currently has no viable alternative for achieving high performance of the final device. Here, it is shown that the novel, ultrathin Ga₂O₃ glass is an ideal centimeter‐scale coating material that enhances optical performance of the monolayers and protects them against further material deposition. In particular, Ga₂O₃ capping of monolayer WS₂ outperforms commercial‐grade hBN in both scalability and optical performance at room temperature. These properties make Ga₂O₃ highly suitable for large‐scale passivation and protection of monolayer TMDCs in functional heterostructures.

Substantial coercivity reduction by the current, larger at least by two orders of magnitude than those in previous reports, is found in the van der Waals ferromagnet Fe₃GeTe₂. It is theoretically shown to arise from an unusual type of gigantic spin–orbit torque, which itself is directly related to its special symmetries, large Berry curvature, and band topology. A working model of a new robust nonvolatile magnetic memory based on Fe₃GeTe₂, controlled by a much smaller current, is also produced.

Abstract

Controlling magnetic states by a small current is essential for the next‐generation of energy‐efficient spintronic devices. However, it invariably requires considerable energy to change a magnetic ground state of intrinsically quantum nature governed by fundamental Hamiltonian, once stabilized below a phase‐transition temperature. Here, it is reported that, surprisingly, an in‐plane current can tune the magnetic state of the nanometer‐thin van der Waals ferromagnet Fe₃GeTe₂ from a hard magnetic state to a soft magnetic state. It is a direct demonstration of the current‐induced substantial reduction of the coercive field. This surprising finding is possible because the in‐plane current produces a highly unusual type of gigantic spin–orbit torque for Fe₃GeTe₂. In addition, a working model of a new nonvolatile magnetic memory based on the principle of the discovery in Fe₃GeTe₂, controlled by a tiny current, is further demonstrated. The findings open up a new window of exciting opportunities for magnetic van der Waals materials with potentially huge impact on the future development of spintronic and magnetic memory.

A rich variety of distinct chemical bonding configurations of a single‐metal atom with its surrounding host atoms creates vast opportunities for the rational design and synthesis of single‐atom electrocatalysts with tunable local atomic environment for high‐performance renewable energy conversions.

Abstract

Single‐atom electrocatalysts (SAECs) have recently attracted tremendous research interest due to their often remarkable catalytic responses, unmatched by conventional catalysts. The electrocatalytic performance of SAECs is closely related to the specific metal species and their local atomic environments, including their coordination number, the determined structure of the coordination sites, and the chemical identity of nearest and second nearest neighboring atoms. The wide range of distinct chemical bonding configurations of a single‐metal atom with its surrounding host atoms creates virtually limitless opportunities for the rational design and synthesis of SAECs with tunable local atomic environment for high‐performance electrocatalysis. In this review, the authors first identify fundamental hurdles in electrochemical conversions and highlight the relevance of SAECs. They then critically examine the role of the local atomic structures, encompassing the first and second coordination spheres of the isolated metal atoms, on the design of high‐performance SAECs. The relevance of single‐atom dopants for host activation is also discussed. Insights into the correlation between local structures of SAECs and their catalytic response are analyzed and discussed. Finally, the authors summarize major challenges to be addressed in the field of SAECs and provide some perspectives in the rational construction of superior SAECs for a wide range of electrochemical conversions.

Ultrathin twisted Ge_{1– x} Sn _x S nanoribbons, realized via scalable vapor–liquid–solid growth over gold catalysts, provide a unique platform for probing guided excitonic waveguide modes in van der Waals semiconductors. Nanophotonic experiments using local electron‐beam excitation detect the confined modes in the plane of the layered crystal and enable the measurement of key properties such as the field distribution into the adjacent cladding layers.

Abstract

Ultrathin van der Waals semiconductors have shown extraordinary optoelectronic and photonic properties. Propagating photonic modes make layered crystal waveguides attractive for photonic circuitry and for studying hybrid light–matter states. Accessing guided modes by conventional optics is challenging due to the limited spatial resolution and poor out‐of‐plane far‐field coupling. Scanning near‐field optical microscopy can overcome these issues and can characterize waveguide modes down to a resolution of tens of nanometers, albeit for planar samples or nanostructures with moderate height variations. Electron microscopy provides atomic‐scale localization also for more complex geometries, and recent advances have extended the accessible excitations from interband transitions to phonons. Here, bottom‐up synthesized layered semiconductor (Ge_{1– x} Sn _x S) nanoribbons with an axial twist and deep subwavelength thickness are demonstrated as a platform for realizing waveguide modes, and cathodoluminescence spectroscopy is introduced as a tool to characterize them. Combined experiments and simulations show the excitation of guided modes by the electron beam and their efficient detection via photons emitted in the ribbon plane, which enables the measurement of key properties such as the evanescent field into the vacuum cladding with nanometer resolution. The results identify van der Waals waveguides operating in the infrared and highlight an electron‐microscopy‐based approach for probing complex‐shaped nanophotonic structures.

Systematic changes of chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S, O) are studied to comprehend their properties. The exploration reveals an electron‐transfer‐driven transition from metavalent bonding in PbX (X = Te, Se, S) to iono‐covalent bonding in β‐PbO. The insights gained from this study highlight the technological relevance of the concept of metavalent bonding and its potential for materials design.

Abstract

Understanding the nature of chemical bonding in solids is crucial to comprehend the physical and chemical properties of a given compound. To explore changes in chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S, O), a combination of property‐, bond‐breaking‐, and quantum‐mechanical bonding descriptors are applied. The outcome of the explorations reveals an electron‐transfer‐driven transition from metavalent bonding in PbX (X = Te, Se, S) to iono‐covalent bonding in β‐PbO. Metavalent bonding is characterized by adjacent atoms being held together by sharing about a single electron (ES ≈ 1) and small electron transfer (ET). The transition from metavalent to iono‐covalent bonding manifests itself in clear changes in these quantum‐mechanical descriptors (ES and ET), as well as in property‐based descriptors (i.e., Born effective charge (Z*), dielectric function ε(ω), effective coordination number (ECoN), and mode‐specific Grüneisen parameter (γ_TO)), and in bond‐breaking descriptors. Metavalent bonding collapses if significant charge localization occurs at the ion cores (ET) and/or in the interatomic region (ES). Predominantly changing the degree of electron transfer opens possibilities to tailor material properties such as the chemical bond (Z*) and electronic (ε_∞) polarizability, optical bandgap, and optical interband transitions characterized by ε₂(ω). Hence, the insights gained from this study highlight the technological relevance of the concept of metavalent bonding and its potential for materials design.

In article number 2005533, Matthias Wuttig and co‐workers study systematic changes of chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S, O) to comprehend their properties. They discover an electron‐transfer‐driven transition from highly anharmonic, metavalent bonding in thermoelectric PbX (X = Te, Se, S) to iono‐covalent bonding in β‐PbO, highlighting the relevance of the concept of metavalent bonding for materials design.

Single crystals of the YbMnSb₂ nodal line semimetal demonstrate the synergetic contribution of Dirac bands and regular band to the thermoelectric performance. A high power factor over 2.1 mW m⁻¹ K⁻² is achieved due to both high mobility and large thermopower.

Abstract

The emerging class of topological materials provides a platform to engineer exotic electronic structures for a variety of applications. As complex band structures and Fermi surfaces can directly benefit thermoelectric performance it is important to identify the role of featured topological bands in thermoelectrics particularly when there are coexisting classic regular bands. In this work, the contribution of Dirac bands to thermoelectric performance and their ability to concurrently achieve large thermopower and low resistivity in novel semimetals is investigated. By examining the YbMnSb₂ nodal line semimetal as an example, the Dirac bands appear to provide a low resistivity along the direction in which they are highly dispersive. Moreover, because of the regular‐band‐provided density of states, a large Seebeck coefficient over 160 µV K⁻¹ at 300 K is achieved in both directions, which is very high for a semimetal with high carrier concentration. The combined highly dispersive Dirac and regular bands lead to ten times increase in power factor, reaching a value of 2.1 mW m⁻¹ K⁻² at 300 K. The present work highlights the potential of such novel semimetals for unusual electronic transport properties and guides strategies towards high thermoelectric performance.

Localized magnetic moments induced by Pt vacancies in air‐stable non‐magnetic PtSe₂ nanoflakes are reported and the induced magnetic moments in PtSe₂ nanoflakes are found to be nearly thickness dependent in thinner nanoflakes. These findings demonstrate a new way to induce magnetism in nonmagnetic 2D materials.

Abstract

2D magnetism plays a key role in both fundamental physics and potential device applications. However, the instability of the discovered 2D magnetic materials has been one main obstacle in deep research and potential application of 2D magnetism. Here, a localized magnetic moment induced by Pt vacancies in air‐stable type‐II Dirac semimetal PtSe₂ flakes is reported. The localized magnetic moments give rise to the Kondo effect, evidenced by logarithmic increment of resistance with decreasing temperature and isotropic negative longitudinal magnetoresistance. Additionally, the induced magnetic moment and Kondo temperature appear to depend on thickness in the thinner samples (<10 nm). The small magnetocrystalline anisotropy revealed by first‐principles calculation indicates that the magnetic moments are randomly localized instead of long‐range ordered. The findings demonstrate a new means to induce magnetism in 2D non‐magnetic materials.

The thermoelectric (TE) transport in few‐layer Bi₂O₂Se is probed, where gating can effectively modulate its scattering mechanism from polar optical phonon to piezoelectric scattering. This facilitates the capacity of drastic mobility engineering, and high TE performance over a wide range of temperature can be achieved due to the persistently high mobility arising from the highly gate‐tunable scattering mechanism.

Abstract

Atomically thin Bi₂O₂Se has emerged as a new member in 2D materials with ultrahigh carrier mobility and excellent air‐stability, showing great potential for electronics and optoelectronics. In addition, its ferroelectric nature renders an ultralow thermal conductivity, making it a perfect candidate for thermoelectrics. In this work, the thermoelectric performance of 2D Bi₂O₂Se is investigated over a wide temperature range (20–300 K). A gate‐tunable transition from polar optical phonon (POP) scattering to piezoelectric scattering is observed, which facilitates the capacity of drastic mobility engineering in 2D Bi₂O₂Se. Consequently, a high power factor of more than 400 µW m⁻¹ K⁻² over an unprecedented temperature range (80–200 K) is achieved, corresponding to the persistently high mobility arising from the highly gate‐tunable scattering mechanism. This finding provides a new avenue for maximizing thermoelectric performance by changing the scattering mechanism and carrier mobility over a wide temperature range.

The thermoelectric (TE) transport in few‐layer Bi₂O₂Se is probed, where gating can effectively modulate its scattering mechanism from polar optical phonon to piezoelectric scattering. This facilitates the capacity of drastic mobility engineering, and high TE performance over a wide range of temperature can be achieved due to the persistently high mobility arising from the highly gate‐tunable scattering mechanism.

Abstract

Atomically thin Bi₂O₂Se has emerged as a new member in 2D materials with ultrahigh carrier mobility and excellent air‐stability, showing great potential for electronics and optoelectronics. In addition, its ferroelectric nature renders an ultralow thermal conductivity, making it a perfect candidate for thermoelectrics. In this work, the thermoelectric performance of 2D Bi₂O₂Se is investigated over a wide temperature range (20–300 K). A gate‐tunable transition from polar optical phonon (POP) scattering to piezoelectric scattering is observed, which facilitates the capacity of drastic mobility engineering in 2D Bi₂O₂Se. Consequently, a high power factor of more than 400 µW m⁻¹ K⁻² over an unprecedented temperature range (80–200 K) is achieved, corresponding to the persistently high mobility arising from the highly gate‐tunable scattering mechanism. This finding provides a new avenue for maximizing thermoelectric performance by changing the scattering mechanism and carrier mobility over a wide temperature range.

A novel van der Waals heterostructure consisting of monolayer MoSe₂, Mn oxide, and a buffer layer (h‐BN) demonstrates magnetic proximity and charge transfer effect for the excitonic states due to phase transition of Mn oxide from ferromagnetic metal to paramagnetic insulator. The controllable thickness of h‐BN reveals a characteristic length scale of several nanometers in magnetic proximity and charge transfer.

Abstract

Optically generated excitonic states (excitons and trions) in transition metal dichalcogenides are highly sensitive to the electronic and magnetic properties of the materials underneath. Modulation and control of the excitonic states in a novel van der Waals (vdW) heterostructure of monolayer MoSe₂ on double‐layered perovskite Mn oxide ((La_0.8Nd_0.2)_1.2Sr_1.8Mn₂O₇) is demonstrated, wherein the Mn oxide transforms from a paramagnetic insulator to a ferromagnetic metal. A discontinuous change in the exciton photoluminescence intensity via dielectric screening is observed. Further, a relatively high trion intensity is discovered due to the charge transfer from metallic Mn oxide under the Curie temperature. Moreover, the vdW heterostructures with an ultrathin h‐BN spacer layer demonstrate enhanced valley splitting and polarization of excitonic states due to the proximity effect of the ferromagnetic spins of Mn oxide. The controllable h‐BN thickness in vdW heterostructures reveals a several‐nanometer‐long scale of charge transfer as well as a magnetic proximity effect. The vdW heterostructure allows modulation and control of the excitonic states via dielectric screening, charge carriers, and magnetic spins.

Janus crystals represent an exciting class of 2D materials with different atomic species on their upper and lower facets. Theories predict that this broken symmetry leads to a wealth of novel properties. A room‐temperature technique for the synthesis of a variety of Janus monolayers and their lateral and vertical heterostructures with high structural and optical quality is reported.

Abstract

Janus crystals represent an exciting class of 2D materials with different atomic species on their upper and lower facets. Theories have predicted that this symmetry breaking induces an electric field and leads to a wealth of novel properties, such as large Rashba spin–orbit coupling and formation of strongly correlated electronic states. Monolayer MoSSe Janus crystals have been synthesized by two methods, via controlled sulfurization of monolayer MoSe₂ and via plasma stripping followed thermal annealing of MoS₂. However, the high processing temperatures prevent growth of other Janus materials and their heterostructures. Here, a room‐temperature technique for the synthesis of a variety of Janus monolayers with high structural and optical quality is reported. This process involves low‐energy reactive radical precursors, which enables selective removal and replacement of the uppermost chalcogen layer, thus transforming classical transition metal dichalcogenides into a Janus structure. The resulting materials show clear mixed character for their excitonic transitions, and more importantly, the presented room‐temperature method enables the demonstration of first vertical and lateral heterojunctions of 2D Janus TMDs. The results present significant and pioneering advances in the synthesis of new classes of 2D materials, and pave the way for the creation of heterostructures from 2D Janus layers.

Substitutional rhenium (Re) doping of tungsten diselenide (WSe₂) films is achieved via metal–organic chemical vapor deposition at front‐end‐of‐line (FEOL) and back‐end‐of‐line (BEOL) compatible temperatures, with a doping concentration of <0.001%. Trion concentration is increased as a function of dopant concentration and discrete donor levels that lie close to the conduction band are observed, confirming the n‐type dopant nature of the rhenium atoms.

Abstract

Reliable, controlled doping of 2D transition metal dichalcogenides will enable the realization of next‐generation electronic, logic‐memory, and magnetic devices based on these materials. However, to date, accurate control over dopant concentration and scalability of the process remains a challenge. Here, a systematic study of scalable in situ doping of fully coalesced 2D WSe₂ films with Re atoms via metal–organic chemical vapor deposition is reported. Dopant concentrations are uniformly distributed over the substrate surface, with precisely controlled concentrations down to <0.001% Re achieved by tuning the precursor partial pressure. Moreover, the impact of doping on morphological, chemical, optical, and electronic properties of WSe₂ is elucidated with detailed experimental and theoretical examinations, confirming that the substitutional doping of Re at the W site leads to n‐type behavior of WSe₂. Transport characteristics of fabricated back‐gated field‐effect‐transistors are directly correlated to the dopant concentration, with degrading device performances for doping concentrations exceeding 1% of Re. The study demonstrates a viable approach to introducing true dopant‐level impurities with high precision, which can be scaled up to batch production for applications beyond digital electronics.

The distinct physical origin of 2D polarizations and modulation on degrees of freedom are comprehensively summarized based on the hysteresis behaviors and interface effects. The novel multifunctional polarized devices are discussed, from which perspectives and guidelines are proposed for developing the “Beyond Moore” integrated devices and circuits.

Abstract

The emergence of 2D polarized materials, including ferromagnetic, ferrovalley, and ferroelectric materials, has demonstrated unique quantum behaviors at atomic scales. These polarization behaviors are tightly bonded to the new degrees of freedom (DOFs) for next generation information storage and processing, which have been dramatically developed in the past few years. Here, the basic 2D polarized materials system and related devices’ application in spintronics, valleytronics, and electronics are reviewed. Specifically, the underlying physical mechanism accompanied with symmetry broken theory and the modulation process through heterostructure engineering are highlighted. These summarized works focusing on the 2D polarization would continue to enrich the cognition of 2D quantum system and promising practical applications.