Jiuxiang Dai

Domain walls are highly intriguing because of their ability to host unique phases at the nanoscale that are absent in the bulk. This study uncovers multiferroic domain walls in a non-multiferroic environment in Dy0.7Tb0.3FeO3. Using advanced optical techniques, the research demonstrates stable yet switchable magnetization and polarization confined to nanoscale walls, distinct from the bulk. This discovery provides critical insights into emergent ferroic phases, enriching the understanding of domain wall physics, and offers new pathways for oxide electronics, such as antiferromagnetic spintronics.

Nature Materials, Published online: 17 March 2025; doi:10.1038/s41563-025-02158-1

Pockels coefficients and permittivity are measured in barium titanate and lithium niobate from 100 MHz to 330 GHz and device geometries are proposed to maintain a constant electro-optic response in BTO devices.

Nature Communications, Published online: 14 March 2025; doi:10.1038/s41467-025-57620-0

Chiral organic-inorganic perovskites are promising materials for circularly polarized luminescence. Here the authors present chiral europium halides leading to red circularly polarized luminescence with large dissymmetry factor and strong magneto-chiroptical properties.

Nature Nanotechnology, Published online: 14 March 2025; doi:10.1038/s41565-025-01884-6

A transistor made from bilayer A-type antiferromagnet CrPS4 provides control over the spin polarization at the Fermi level and magnetoelectric readout.

Nature Communications, Published online: 16 March 2025; doi:10.1038/s41467-025-57773-y

2D high-κ dielectric materials remain highly sought-after for the future development of 2D electronics. Here, the authors report a 2D edge-seeded heteroepitaxial growth strategy to synthesize CaNb2O6 thin films with equivalent oxide thickness down to 0.7 nm and show their application for high-performance 2D MoS2 transistors.

Employing a two-step synthesis approach, a library of high-entropy metal sulfide (HEMS) materials spanning quinary to duodenary compositions are built by arbitrarily combining 5–12 elements from 28 candidates in the periodic table. The septenary HEMS particles exhibit remarkable cycling stability—retaining≈230 mAh g⁻¹ over 3000 cycles—attributed to uniform metal mixing during discharge.

Abstract

Controlled synthesis of high-entropy materials offers a unique platform to explore unprecedented electrochemical properties. High-entropy metal sulfides (HEMSs) have recently emerged as promising electrodes in electrochemical energy storage applications. However, synthesizing HEMSs with a tunable number of components and composition is still challenging. Here, a HEMS library is built by using a general synthetic approach, enabling the synthesis of HEMS with arbitrary combinations of 5 to 12 out of 28 elements in the periodic table. The formation of a solid solution of HEMS is attributed to the two-step method that lowers the energy barrier and facilitates the sulfur diffusion during the synthesis. The hard soft acid base (HSAB) theory is used to precisely describe the conversion rates of the metal precursors during the synthesis. The HEMSs as cathodes in Na-ion batteries (SIBs) is investigated, where 7-component HEMS (7-HEMS) delivers a promising rate capability and an exceptional sodium storage performance with reversible a capacity of 230 mAh g⁻¹ over 3000 cycles. This work paves the way for the multidisciplinary exploration of HEMSs and their potential in electrochemical energy storage.

S-atoms are selected as donor dopants to achieve the n-type conductivity of the hBN film. A theoretical model of S-doping hBN using DFT calculation and experimentally prepared S-doped hBN multilayers with a recorded doping concentration of 1.21% is established. Combining with Mg-doped hBN films, a vertically-stacked n-hBN/p-hBN homojunction, which shows the superiority of deep-UV light-emitting is constructed.

Abstract

A hexagonal boron nitride (hBN) based p-n homo-junction is expected to demonstrate a great potential for being fabricated into an emitter (either light-emitting diode or laser diode) in the deep-UV spectral region. However, it remains a great challenge to achieve n-type conductive hBN. Herein, n-type hBN is obtained by means of doping sulfur into hBN. The structure and the electric properties of S-doped hBN is studied via density functional theory, indicating that the orbital coupling between S 3p and B 2p orbital introduces shallow donor energy levels. The S atoms in the multilayer structure demonstrate enhanced electron delocalization compared with its mono-layer counterpart, suggesting that multilayer hBN:S is more inclined to be n-type conductive than its mono-layer counterpart. Experimentally, a multilayer hBN:S sample is successfully grown on sapphire substrates, where the S content, up to 1.21%, is obtained. The hBN:S film shows an in-plane current of 1.6 nA using Ti as ohmic contact and 8.4 nA using Ni as Schottky contact, respectively. The donor level induced by the S atoms is located at 0.349 eV below the CBM. Finally, a vertically-stacked n-hBN/p-hBN (hBN:S/hBN: Mg) structured junction is grown, and demonstrating a promise for being fabricated into a deep-UV emitter.

This study focuses on exploring the nonlinear optical properties of α-Fe₂O₃ material calcined at ultra-high temperatures. It is discovered that the α-Fe₂O₃ material underwent the phase transition at ultra-high temperatures. Then, the α-Fe₂O₃ material calcined at 1100 °C is successfully integrated as a saturable absorber into an erbium-doped fiber laser, achieving conventional soliton mode-locking operation and dissipative soliton resonance mode-locking operation within the C-band.

Abstract

As a typical transition metal oxide, α-Fe₂O₃ has garnered significant attention due to its advantages in nonlinear optical applications, such as strong third-order nonlinearity and fast carrier recovery time. To delve into the nonlinear optical properties of α-Fe₂O₃, crystalline α-Fe₂O₃ materials with different microstructures are prepared. The nonlinear optical features of α-Fe₂O₃ calcined at the previously unexplored ultra-high temperature of >1100°C are emphasized. It is found that α-Fe₂O₃ exposed to ultra-high temperatures undergoes the phase transition, leading to the formation of Fe₃O₄. Subsequently, the nonlinear absorption coefficient is measured as −0.6280 cm GW⁻¹ at 1.5 µm. The modulation depth and saturation intensity for the Fe₂O₃-based saturable absorber at 1.5 µm are 4.20% and 13.94 MW cm⁻², respectively. Ultimately, the incorporation of the Fe₂O₃-based saturable absorber into an Er-doped fiber laser cavity resulted in the achievement of both conventional soliton mode-locking operation with a central wavelength of 1560.3 nm and a pulse duration of 1.13 ps, as well as the dissipative soliton resonance mode-locking operation with a central wavelength near 1564.0 nm. Overall, the phase transition and the nonlinear optical features in iron oxides under ultra-high temperatures are revealed, indicating the great potential in advanced ultrafast photonic applications.

This review examines advancements in 2D materials, focusing on their applications in piezotronics and piezo-phototronics. It discusses key materials like TMDs, h-BN, and phosphorene, highlighting their unique mechanical, electronic, and optical properties. The review delves into the mechanisms of piezoelectricity, explores applications such as nanogenerators and biomedical devices, and describes the future and challenges in 3D integration of 2D materials.

Abstract

The emergence of two-dimensional (2D) materials has catalyzed significant advancements in the fields of piezotronics and piezo-phototronics, owing to their exceptional mechanical, electronic, and optical properties. This review provides a comprehensive examination of key 2D piezoelectric and piezo-phototronic materials, including transition metal dichalcogenides, hexagonal boron nitride (h-BN), and phosphorene, with an emphasis on their unique advantages and recent research progress. The underlying principles of piezotronics and piezo-phototronics in 2D materials is discussed, focusing on the fundamental mechanisms which enable these phenomena. Additionally, it is analyzed factors affecting piezoelectric and piezo-photoelectric properties, with a particular focus on the intrinsic piezoelectricity of 2D materials and the enhancement of out-of-plane polarization through various modulation techniques and materials engineering approaches. The potential applications of these materials are explored from piezoelectric nanogenerators to piezo-phototronic devices and healthcare. This review addresses future challenges and opportunities, highlighting the transformative impact of 2D materials on the development of next-generation electronic, optoelectronic, and biomedical devices.

This work introduces a doping strategy for harvesting ultrathin Ga oxide layers using a multi-elemental Ga-based liquid metal alloy. The incorporation of trivalent In metal into the self-limiting oxide formed on the alloy's surface is enabled by the existence of atomically dispersed Pt, Au, and Pd.

Abstract

The naturally self-limiting oxide formed on the surface of liquid metals can be exfoliated and transferred onto various substrates. This oxide layer with a thickness of a few nanometers is typically highly transparent and can be engineered for applications in large-area optoelectronics. While the incorporation of solvated elements into the interfacial oxide of post-transition metal-based liquid metals is demonstrated for n-doping, achieving p-doping in such ultrathin oxide layers remains a significant challenge. In this study, the use of dissolved indium (In), platinum (Pt), gold (Au), palladium (Pd), and copper (Cu) in gallium (Ga)-based alloys is investigated to create a high-entropy liquid metal system. This allows the exfoliation of a p-doped ultrathin oxide layer, predominantly composed of gallium oxide (Ga₂O₃). The incorporation of these post-transition metals in this high-entropy system results in their atomic dispersion, with Cu exhibiting limited surface presence. The atomically dispersed Pt, Au, and Pd metals scavenge oxygen during exfoliation at moderate temperatures and release them during cooling down, promoting the emergence of trivalent metallic In in Ga oxide layer. This work presents a novel doping strategy at moderate temperatures to achieve p-doped liquid-metal-derived ultrathin Ga₂O₃ layers, which maintain high transparency.

Bulk single crystals of non-centrosymmetric 3R-TaSe₂ are first grown, and show intrinsic superconductivity of T _c = 2.89 K with Pauli-violated upper critical field. As thickness reduces, Ising superconductivity protected by spin-valley locking, and orbital Fulde–Ferrell–Larkin–Ovchinnikov states gradually emerge due to the interplay between sizable spin-orbital coupling and interlayer orbital hopping.

Abstract

Layered superconductors without inversion symmetry exhibit fantastic phenomena like spin-triplet, Ising pairing, and non-zero momentum of Cooper pairs. Identifying such unique compound and achieving accessible single crystals are rather challenging. Here, the sizable 3R-TaSe₂ single crystals are first grown upon precisely controlling the temperature gradient, and then its superconducting properties are studied as reducing thickness. The bulk 3R-TaSe₂ shows 3 × 3 charge-density-wave (CDW) transition at 114 K and superconductivity at 2.89 K. Its in-plane upper critical field (Hc2ab$H_{c2}^{ab}$) is two times of Pauli-limited value (H _p). Contrasting with the three-fold symmetric lattice, the superconducting state exhibits a two-fold rotational symmetry under in-plane external magnetic fields, implying the possible s+p/d mixed states. More importantly, in two unit-cells (UC) 3R-TaSe₂, the Hc2ab$H_{c2}^{ab}$ >3H _p and the square-root relation of Hc2ab$H_{c2}^{ab}$-T near T _c are hallmarks of Ising SC. In 4 UC and 8 UC flakes, orbital Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) states emerged between (T ^*, H ^*) = (0.91 T _c0, 0.37 H _p) and (T ^*, H ^*) = (0.76T _c0, 0.94 H _p). It can be explained by the indispensably interlayer orbital hopping under the context of Ising pairing. The results set the 3R-TaSe₂ as a platform to study the role of interplay between orbits and spins in electronically ordered states.

An in situ on-device synthesis process is developed. First, PdTe₂ is exfoliated into thin flakes and fabricated into a transport device. Subsequently, an electrochemical process is carried out on this device to in situ intercalate Pd⁴⁺ into the van der Waals gaps, thus transferring the layered material PdTe₂ to non-layered material PdTe, forming a high-quality pure PdTe flake device.

Abstract

Transition metal chalcogenides (TMCs) are emerging as platforms for exploring exotic phenomena such as topological physics and superconductivity. PdTe, as one of such materials, has recently been regarded as a candidate for Dirac semimetal and unconventional superconductivity. The superconducting behavior of PdTe from the bulk and the surface varies, thus a comparison between PdTe thin flakes and bulk materials is necessary. Due to the scarcity of reports on pure PdTe thin flakes, this study develops an in situ on-device synthesis process. First, a PdTe₂ bulk is exfoliated into thin flakes and fabricated into a transport device. Subsequently, an electrochemical process is carried out on this device to in situ transform the layered material PdTe₂ to non-layered material PdTe, forming a high-quality pure PdTe flake device. The critical temperature onset (TConset$T_{\mathrm{C}}^{{\mathrm{onset}}}$) of the flake (≈3.2 K) is lower than that of the bulks (≈4.4 K), while the values and the anisotropy of the upper critical fields (H _C2) are enhanced, demonstrating the characteristics of 2D superconductivity which are distinct from those of the bulks. This work provides a platform for studying the superconductivity of PdTe thin flakes and offers an approach for investigating candidates for unconventional superconductivity.

Magneto-ferroelectric effects in van der Waals EuO/graphene heterostructures emerge via a topotactic method, inducing high compressive strain. This strain stabilizes a ferroelectric state up to room temperature, coexisting with the magnetic proximity effect in graphene. These intertwined magneto-electric effects enable control of magnetization and polarization, offering the potential for next-gen memory and neuromorphic devices.

Abstract

2D van der Waals materials and their heterostructures are a fantastic playground to explore emergent phenomena arising from electronic quantum hybridization effects. In the last decade, the spin-dependant hybridization effect pushed this frontier further introducing the magnetic proximity effect as a promising tool for spintronic applications. Here the uncharted proximity-controlled magnetoelectric effect in EuO/graphene heterostructure is unveiled. This is obtained while creating a new multiferroic hybrid heterostructure with multifunctional properties. Using a topotactic method magnetic insulating EuO thin films on graphene is grown under high compressive strain, which induces the appearance of an additional ferroelectric order, with an electric polarization that reaches up to 18 µC cm⁻² at room temperature. This observation therefore quantitatively confirms the theoretical predictions made 15 years ago of a strain-induced ferroelectric state in EuO. Moreover, the EuO induces a magnetic proximity state into the graphene layer by interfacial hybridization. This new ferroelectric state in the EuO/graphene heterostructure is stable up to room temperature where it coexists with the EuO/graphene magnetic state. Furthermore, intertwined magneto-electric effects are shown in these strained heterostructures which can facilitate the manipulation of magnetization and electric polarization in future memory and neuromorphic devices.

Nature, Published online: 12 March 2025; doi:10.1038/s41586-025-08711-x

Melting and squeezing pure metals between two sapphires covered in molybdenum disulfide produces diverse two-dimensional metals at the ångström thickness limit.

Nature, Published online: 12 March 2025; doi:10.1038/s41586-024-08563-x

Phosphorene nanoribbons demonstrate extraordinary magnetic properties, ranging from large internal fields in films to macroscopic alignment in solution, which can be coupled to photoexcitations that localize to the magnetic edge of these ribbons.

Nature, Published online: 12 March 2025; doi:10.1038/s41586-025-08666-z

An optical parametric amplifier based on integrated photonic circuits fabricated using low-loss gallium phosphide-on-silicon dioxide demonstrates improved bandwidth and gain performance over state-of-the-art erbium-doped fibre amplifiers while maintaining a low noise figure.

Current organic light-emitting diode (OLED) technology uses light-emitting molecules in a molecular host. We report green circularly polarized luminescence (CPL) in a chirally ordered supramolecular assembly, with 24% dissymmetry in a triazatruxene (TAT) ...

Author(s): Mingqiang Gu, Yuntian Liu, Haiyuan Zhu, Kunihiro Yananose, Xiaobing Chen, Yongkang Hu, Alessandro Stroppa, and Qihang Liu

Researchers have proposed methods to tune the properties of altermagnets, a step toward practical applications for this new form of magnet.

[Phys. Rev. Lett. 134, 106802] Published Thu Mar 13, 2025

Stepwise vacancy manipulation including changing Cu content and doping Bi element significantly improves the thermoelectric performance of CuInTe₂-based materials, with the highest zT value reaching 1.8 at 773 K, which is almost three times that of the pristine CuInTe₂, setting a new record for zT value in the CuInTe₂ materials.

Abstract

Great enhancement in the thermoelectric performance of CuInTe₂ is achieved through stepwise regulation of Cu vacancies. Lowering Cu content can effective introduce large number of Cu vacancies, which is substantiated by positron annihilation measurements. The carrier concentration is thereby successfully tuned from 5.5× 10¹⁸ cm⁻³ to 3.2× 10¹⁹ cm⁻³. The Cu vacancies strongly suppress the lattice thermal conductivity due to both enhanced phonon scattering and lowered phonon velocity. As a consequence, a high zT value exceeding 1.2 at 773 K is achieved in Cu_0.95InTe₂ with optimal carrier concentration of 1.65× 10¹⁹ cm⁻³. The highly Cu deficient Cu_0.90InTe₂ sample is further doped with Bi, which can fill the excessive Cu vacancies. The Bi dopants introduce mass and strain fluctuation, and also cause modulation of lattice structure to form ordered superstructures, which all enhance phonon scattering. In addition, Bi doping results in severe lattice softening, which significantly reduces phonon velocity. As a result, an extremely low lattice thermal conductivity of 1.19 W m⁻¹ K⁻¹ is reached at 300 K. Eventually, a record high zT value of 1.8 at 773 K is achieved in the Cu_0.90Bi_0.06InTe₂ sample, which is almost three times that of the pristine CuInTe₂, reaching the leading level for CuInTe₂-based materials.

This study presents an Au/WS₂/WSe₂/Au memristor with type-II band alignment. The interlayer coupling within this heterostructure is tuned by annealing at different temperatures. Notably, annealing at 350 °C significantly strengthens the interlayer interactions, leading to a marked enhancement in the memristor's electrical performance, which is supported by first-principles density functional theory. The enhanced memristor also exhibits decent synaptic plasticity.

Abstract

Few-layered 2D materials are promising candidates to build highly integrated memristors. The interlayer coupling between two different 2D materials in heterostructure is crucial for their band structure modulation. In this study, an Au/WS₂/WSe₂/Au van der Waals heterostructure memristor is reported, the type-II band alignment heterostructure formed by few-layered WS₂ and WSe₂. The interlayer coupling of the heterostructure is tuned by annealing at different temperatures under argon atmosphere. The switching ratio and I–V cycle number of the memristor annealed at 350 °C is increased to 10⁵ and 300, which are 1000 times and 6 times that of unannealed memristor, respectively. The first-principle density functional theory (DFT) calculations indicate that the enhanced interlayer coupling caused by annealing significantly reduces the bandgap of heterojunction under applied voltage, thereby improving the electrical performance of the memristor. Additionally, the memristor exhibits notable synaptic plasticity, and simulations applied in the handwritten digit recognition classification achieve the highest accuracy of 92%. This work highlights a novel approach for improving the performance of memristors based on 2D heterostructure by tuning the interlayer coupling of the heterojunction.

A mechanism is proposed to realize triferroic order coexistence and multiple types of valley polarization by structural phase transition in 2D materials. Interestingly, the 1T phase OsBr₂ bilayer shows the tri-state valley polarization due to lattice symmetry breaking, while the valley polarization of 2H phase bilayer originates from the combined effect of time-reversal symmetry breaking and spin-orbit coupling.

Abstract

The multiferroic materials, which coexist magnetism, ferroelectric, and ferrovalley, have broad practical application prospects in promoting the miniaturization and integration of spintronic and valleytronic devices. However, it is rare that there are triferroic orders and multiple types of valley polarization in a real material. Here, a mechanism is proposed to realize triferroic order coexistence and multiple types of valley polarization by structural phase transition in 2D materials. The 1T and 2H phase OsBr₂ monolayers exhibit non-magnetic semiconductor and ferromagnetic semiconductor with valley polarization up to 175.49 meV, respectively. Interestingly, the 1T phase OsBr₂ bilayer shows the tri-state valley polarization due to lattice symmetry breaking, while the valley polarization of 2H phase bilayer originates from the combined effect of time-reversal symmetry breaking and spin-orbit coupling. Furthermore, the valley polarization and ferroelectric polarization of 1T phase AB stackings and 2H phase AA stackings can be manipulated via interlayer sliding. Importantly, it is verified that the 2H phase can be transformed to 1T phase by Li⁺ ion intercalation, while the 2H phase can occur the structural phase transition into the 1T phase by infrared laser induction. This work provides a feasible strategy for manipulating valley polarization and a design idea for nano-devices with nonvolatile multiferroic properties.

Nature Communications, Published online: 12 March 2025; doi:10.1038/s41467-025-57746-1

Li et al. report ZnF2 as the additive to balance shell growth rate of ZnSe in large InAs/InP/ZnSe/ZnS core-multishell quantum dots. An in-situ photo-crosslinking blended hole-transport layer is used to modulate the energy levels for balanced carrier dynamics in NIR LEDs, enabling peak efficiency of 20.5% and operational half-lifetime of 550 h at 50 W sr−1 m−2.