High-energy-density rechargeable lithium batteries are being pursued by researchers because of their revolutionary potential nature. Current advanced practical lithium-ion batteries have an energy density of around 300 W⋅h⋅kg−1. Continuing to increase the energy density of batteries to a higher level could lead to a major explosion development in some fields, such as electric aviation. Here, we have manufactured practical pouch-type rechargeable lithium batteries with both a gravimetric energy density of 711.3 W⋅h⋅kg−1 and a volumetric energy density of 1653.65 W⋅h⋅L−1. This is achieved through the use of high-performance battery materials including high-capacity lithium-rich manganese-based cathode and thin lithium metal anode with high specific energy, combined with extremely advanced process technologies such as high-loading electrode preparation and lean electrolyte injection. In this battery material system, the structural stability of cathode material in a widened charge/discharge voltage range and the deposition/dissolution behavior of interfacial modified thin lithium electrode are studied.
ISSN: 1741-3540
Chinese Physics Letters provides rapid publication of short reports and important research in all fields of physics.
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Wenkai Zhu et al 2022 Chinese Phys. Lett. 39 128501
A magnetic tunnel junction (MTJ) is the core component in memory technologies, such as the magnetic random-access memory, magnetic sensors and programmable logic devices. In particular, MTJs based on two-dimensional van der Waals (vdW) heterostructures offer unprecedented opportunities for low power consumption and miniaturization of spintronic devices. However, their operation at room temperature remains a challenge. Here, we report a large tunnel magnetoresistance (TMR) of up to 85% at room temperature (T = 300 K) in vdW MTJs based on a thin (< 10 nm) semiconductor spacer WSe2 layer embedded between two Fe3GaTe2 electrodes with intrinsic above-room-temperature ferromagnetism. The TMR in the MTJ increases with decreasing temperature up to 164% at T = 10 K. The demonstration of TMR in ultra-thin MTJs at room temperature opens a realistic and promising route for next-generation spintronic applications beyond the current state of the art.
Shibo Xu et al 2023 Chinese Phys. Lett. 40 060301
Non-Abelian anyons are exotic quasiparticle excitations hosted by certain topological phases of matter. They break the fermion-boson dichotomy and obey non-Abelian braiding statistics: their interchanges yield unitary operations, rather than merely a phase factor, in a space spanned by topologically degenerate wavefunctions. They are the building blocks of topological quantum computing. However, experimental observation of non-Abelian anyons and their characterizing braiding statistics is notoriously challenging and has remained elusive hitherto, in spite of various theoretical proposals. Here, we report an experimental quantum digital simulation of projective non-Abelian anyons and their braiding statistics with up to 68 programmable superconducting qubits arranged on a two-dimensional lattice. By implementing the ground states of the toric-code model with twists through quantum circuits, we demonstrate that twists exchange electric and magnetic charges and behave as a particular type of non-Abelian anyons, i.e., the Ising anyons. In particular, we show experimentally that these twists follow the fusion rules and non-Abelian braiding statistics of the Ising type, and can be explored to encode topological logical qubits. Furthermore, we demonstrate how to implement both single- and two-qubit logic gates through applying a sequence of elementary Pauli gates on the underlying physical qubits. Our results demonstrate a versatile quantum digital approach for simulating non-Abelian anyons, offering a new lens into the study of such peculiar quasiparticles.
Shunli Ni et al 2021 Chinese Phys. Lett. 38 057403
We systematically measure the superconducting (SC) and mixed state properties of high-quality CsV3Sb5 single crystals with Tc ∼ 3.5 K. We find that the upper critical field Hc2(T) exhibits a large anisotropic ratio of at zero temperature and fitting its temperature dependence requires a minimum two-band effective model. Moreover, the ratio of the lower critical field, , is also found to be larger than 1, which indicates that the in-plane energy dispersion is strongly renormalized near Fermi energy. Both Hc1(T) and SC diamagnetic signal are found to change little initially below Tc ∼ 3.5 K and then to increase abruptly upon cooling to a characteristic temperature of ∼2.8 K. Furthermore, we identify a two-fold anisotropy of in-plane angular-dependent magnetoresistance in the mixed state. Interestingly, we find that, below the same characteristic T ∼ 2.8 K, the orientation of this two-fold anisotropy displays a peculiar twist by an angle of 60° characteristic of the Kagome geometry. Our results suggest an intriguing superconducting state emerging in the complex environment of Kagome lattice, which, at least, is partially driven by electron-electron correlation.
Cong Liu et al 2022 Chinese Phys. Lett. 39 076101
Helium is the second most abundant element in the universe, and together with silica, they are important components of giant planets. Exploring the reactivity and state of helium and silica under high pressure is crucial for understanding of the evolution and internal structure of giant planets. Here, using first-principles calculations and crystal structure predictions, we identify four stable phases of a helium-silica compound with seven/eight-coordinated silicon atoms at pressure of 600–4000 GPa, corresponding to the interior condition of the outer planets in the solar system. The density of HeSiO2 agrees with current structure models of the planets. This helium-silica compound exhibits a superionic-like helium diffusive state under the high-pressure and high-temperature conditions along the isentropes of Saturn, a metallic fluid state in Jupiter, and a solid state in the deep interiors of Uranus and Neptune. These results show that helium may affect the erosion of the rocky core in giant planets and may help to form a diluted core region, which not only highlight the reactivity of helium under high pressure but also provide evidence helpful for building more sophisticated interior models of giant planets.
Qiangwei Yin et al 2021 Chinese Phys. Lett. 38 037403
We report the discovery of superconductivity and detailed normal-state physical properties of RbV3Sb5 single crystals with V kagome lattice. RbV3Sb5 single crystals show a superconducting transition at Tc ∼ 0.92 K. Meanwhile, resistivity, magnetization and heat capacity measurements indicate that it exhibits anomalies of properties at T* ∼ 102–103 K, possibly related to the formation of charge ordering state. When T is lower than T*, the Hall coefficient RH undergoes a drastic change and sign reversal from negative to positive, which can be partially explained by the enhanced mobility of hole-type carriers. In addition, the results of quantum oscillations show that there are some very small Fermi surfaces with low effective mass, consistent with the existence of multiple highly dispersive Dirac band near the Fermi energy level.
Yang Shen et al 2023 Chinese Phys. Lett. 40 127401
High-Tc superconductivity with possible Tc ≈ 80 K has been reported in the single crystal of La3Ni2O7 under high pressure. Based on the electronic structure given by the density functional theory calculations, we propose an effective bi-layer model Hamiltonian including both 3dz2 and 3dx2–y2 orbital electrons of the nickel cations. The main feature of the model is that the 3dz2 electrons form inter-layer σ-bonding and anti-bonding bands via the apical oxygen anions between the two layers, while the 3dx2–y2 electrons hybridize with the 3dz2 electrons within each NiO2 plane. The chemical potential difference of these two orbital electrons ensures that the 3dz2 orbitals are close to half-filling and the 3dx2–y2 orbitals are near quarter-filling. The strong on-site Hubbard repulsion of the 3dz2 orbital electrons gives rise to an effective inter-layer antiferromagnetic spin super-exchange J. Applying pressure can self dope holes on the 3dz2 orbitals with the same amount of electrons doped on the 3dx2–y2 orbitals. By performing numerical density-matrix renormalization group calculations on a minimum setup and focusing on the limit of large J and small doping of 3dz2 orbitals, we find the superconducting instability on both the 3dz2 and 3dx2–y2 orbitals by calculating the equal-time spin singlet pair–pair correlation function. Our numerical results may provide useful insights in the high-Tc superconductivity in single crystal La3Ni2O7 under high pressure.
Guangyu Wang et al 2023 Chinese Phys. Lett. 40 077301
Two-dimensional van der Waals magnetic materials are of great current interest for their promising applications in spintronics. Using density functional theory calculations in combination with the maximally localized Wannier functions method and the magnetic anisotropy analyses, we study the electronic and magnetic properties of MnPSe3 monolayer. Our results show that it is a charge transfer antiferromagnetic (AF) insulator. For this Mn2+ 3d5 system, although it seems straightforward to explain the AF ground state using the direct exchange, we find that the nearly 90° Mn–Se–Mn charge transfer type superexchange plays a dominant role in stabilizing the AF ground state. Moreover, our results indicate that, although the shape anisotropy favors an out-of-plane spin orientation, the spin-orbit coupling (SOC) leads to the experimentally observed in-plane spin orientation. We prove that the actual dominant contribution to the magnetic anisotropy comes from the second-order perturbation of the SOC, by analyzing its distribution over the reciprocal space. Using the AF exchange and anisotropy parameters obtained from our calculations, our Monte Carlo simulations give the Néel temperature TN = 47 K for MnPSe3 monolayer, which agrees with the experimental 40 K. Furthermore, our calculations show that under a uniaxial tensile (compressive) strain, Néel vector would be parallel (perpendicular) to the strain direction, which well reproduces the recent experiments. We also predict that TN would be increased by a compressive strain.
Yan Gong et al 2019 Chinese Phys. Lett. 36 076801
An intrinsic magnetic topological insulator (TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remained elusive experimentally for a long time. Here we report the experimental realization of thin films of an intrinsic magnetic TI, MnBi2Te4, by alternate growth of a Bi2Te3 quintuple layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators at higher temperature and in a well-controlled way.
Wang Qing-Yan et al 2012 Chinese Phys. Lett. 29 037402
We report high transition temperature superconductivity in one unit-cell (UC) thick FeSe films grown on a Se-etched SrTiO3 (001) substrate by molecular beam epitaxy (MBE). A superconducting gap as large as 20 meV and the magnetic field induced vortex state revealed by in situ scanning tunneling microscopy (STM) suggest that the superconductivity of the 1 UC FeSe films could occur around 77 K. The control transport measurement shows that the onset superconductivity temperature is well above 50 K. Our work not only demonstrates a powerful way for finding new superconductors and for raising TC, but also provides a well-defined platform for systematic studies of the mechanism of unconventional superconductivity by using different superconducting materials and substrates.
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Ziheng Lan et al 2024 Chinese Phys. Lett. 41 050301
Lee–Yang theory clearly demonstrates where the phase transition of many-body systems occurs and the asymptotic behavior near the phase transition using the partition function under complex parameters. The complex parameters make the direct investigation of Lee–Yang theory in practical systems challenging. Here we construct a non-Hermitian quantum system that can correspond to the one-dimensional Ising model with imaginary parameters through the equality of partition functions. By adjusting the non-Hermitian parameter, we successfully obtain the partition function under different imaginary magnetic fields and observe the Lee–Yang zeros. We also observe the critical behavior of free energy in vicinity of Lee–Yang zero that is consistent with theoretical prediction. Our work provides a protocol to study Lee–Yang zeros of the one-dimensional Ising model using a single-qubit non-Hermitian system.
Meng-Jun Hu et al 2024 Chinese Phys. Lett. 41 050302
Research of Maxwell demon and quantum entanglement is important because of its foundational significance in physics and its potential applications in quantum information. Previous studies on the Maxwell demon have primarily focused on thermodynamics, taking into account quantum correlations. Here we consider from another perspective and ask whether quantum non-locality correlations can be simulated by performing work. The Maxwell demon-assisted Einstein–Podolsky–Rosen (EPR) steering is thus proposed, which implies a new type of loophole. The application of Landauer's erasure principle suggests that the only way to close this loophole during a steering task is by continuously monitoring the heat fluctuation of the local environment by the participant. We construct a quantum circuit model of Maxwell demon-assisted EPR steering, which can be demonstrated by current programmable quantum processors, such as superconducting quantum computers. Based on this quantum circuit model, we obtain a quantitative formula describing the relationship between energy dissipation due to the work of the demon and quantum non-locality correlation. The result is of great physical interest because it provides a new way to explore and understand the relationship between quantum non-locality, information, and thermodynamics.
Bo Li et al 2024 Chinese Phys. Lett. 41 053201
Fano resonance is a ubiquitous phenomenon, and it is commonly interpreted as a two-channel interference of the discrete and continuous channels. The present work investigates the Fano profile from a perspective of the temporal evolution of the wave function. By exciting the atom with a δ pulse and calculating the evolution of the wave function, the Fano formula is deduced. The results clearly show that the Fano resonance is of a three-channel interference, which is different from the traditional understanding. The three channels are revealed as the ground-continuum, ground-discrete-continuum, and a previously unmentioned third channel, i.e., ground-continuum-discrete-continuum. The present three-channel interpretation can be easily generalized to other physical systems, contributing to a deeper understanding of the Fano profile.
Zi-Peng Xu et al 2024 Chinese Phys. Lett. 41 054201
An all-fiber polarization maintaining high-power laser system operating at 1.7 μm based on the Raman-induced soliton self-frequency shifting effect is demonstrated. The entirely fiberized system is built by erbium-doped oscillator and two-stage amplifiers with polarization maintaining commercial silica fibers and devices, which can provide robust and stable soliton generation. High-power soliton laser with the average power of 0.28 W, the repetition rate of 42.7 MHz, and pulse duration of 515 fs is generated directly from the main amplifier. Our experiment provides a feasible method for high-power all-fiber polarization maintaining femtosecond laser generation working at 1.7 μm.
Peng Shi et al 2024 Chinese Phys. Lett. 41 055201
Quasi-coherent micro-instabilities is one of the key topics of magnetic confinement fusion. This work focuses on the quasi-coherent spectra of ion temperature gradient (ITG) and trapped-electron-mode instabilities using newly developed far-forward collective scattering measurements within ohmic plasmas in the J-TEXT tokamak. The ITG mode is characterized by frequencies ranging from 30 to 100 kHz and wavenumbers (kθρs) less than 0.3. Beyond a critical plasma density threshold, the ITG mode undergoes a bifurcation, which is marked by a reduction in frequency and an enhancement in amplitude. Concurrently, enhancements in ion energy loss and degradation in confinement are observed. This ground-breaking discovery represents the first instance of direct experimental evidence that establishes a clear link between ITG instability and ion thermal transport.
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Hai-Yang Ma et al 2024 Chinese Phys. Lett. 41 047103
We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe. Based on first-principles density functional theory calculations, we study the electronic structures, Fermi-surface quantum fluctuations, as well as phonon properties of the antiferromagnetic kagome metal FeGe. It is found that charge density wave emerges in such a system due to a subtle cooperation between electron–electron interactions and electron–phonon couplings, which gives rise to an unusual scenario of interaction-triggered phonon instabilities, and eventually yields a charge density wave (CDW) state. We further show that, in the CDW phase, the ground-state current density distribution exhibits an intriguing star-of-David pattern, leading to flux density modulation. The orbital fluxes (or current loops) in this system emerge as a result of the subtle interplay between magnetism, lattice geometries, charge order, and spin-orbit coupling (SOC), which can be described by a simple, yet universal, tight-binding theory including a Kane–Mele-type SOC term and a magnetic exchange interaction. We further study the origin of the peculiar step-edge states in FeGe, which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.
Xiao Liu et al 2024 Chinese Phys. Lett. 41 047301
Surface acoustic wave (SAW) is a powerful technique for investigating quantum phases appearing in two-dimensional electron systems. The electrons respond to the piezoelectric field of SAW through screening, attenuating its amplitude, and shifting its velocity, which is described by the relaxation model. In this work, we systematically study this interaction using orders of magnitude lower SAW amplitude than those in previous studies. At high magnetic fields, when electrons form highly correlated states such as the quantum Hall effect, we observe an anomalously large attenuation of SAW, while the acoustic speed remains considerably high, inconsistent with the conventional relaxation model. This anomaly exists only when the SAW power is sufficiently low.
Mingfa Tang et al 2024 Chinese Phys. Lett. 41 053102
We report a linear-scaling random Green's function (rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H2O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H2O clusters at T = 0 K can reach an error of ∼ 1 meV per H2O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.
Xingqian Chen et al 2024 Chinese Phys. Lett. 41 037305
SnO2 films exhibit significant potential as cost-effective and high electron mobility substitutes for In2O3 films. In this study, Li is incorporated into the interstitial site of the SnO2 lattice resulting in an exceptionally low resistivity of 2.028 × 10−3 Ω⋅cm along with a high carrier concentration of 1.398 × 1020 cm−3 and carrier mobility of 22.02 cm2/V⋅s. Intriguingly, Lii readily forms in amorphous structures but faces challenges in crystalline formations. Furthermore, it has been experimentally confirmed that Lii acts as a shallow donor in SnO2 with an ionization energy ΔED1 of −0.4 eV, indicating spontaneous occurrence of Lii ionization.
Jiawei Hu et al 2024 Chinese Phys. Lett. 41 037401
Moiré superlattices in twisted two-dimensional materials have emerged as ideal platforms for engineering quantum phenomena, which are highly sensitive to twist angles, including both the global value and the spatial inhomogeneity. However, only a few methods provide spatial-resolved information for characterizing local twist angle distribution. Here we directly visualize the variations of local twist angles and angle-dependent evolutions of the quantum states in twisted bilayer graphene by scanning microwave impedance microscopy (sMIM). Spatially resolved sMIM measurements reveal a pronounced alteration in the local twist angle, approximately 0.3° over several micrometers in some cases. The variation occurs not only when crossing domain boundaries but also occasionally within individual domains. Additionally, the full-filling density of the flat band experiences a change of over 2 × 1011 cm−2 when crossing domain boundaries, aligning consistently with the twist angle inhomogeneity. Moreover, the correlated Chern insulators undergo variations in accordance with the twist angle, gradually weakening and eventually disappearing as the deviation from the magic angle increases. Our findings signify the crucial role of twist angles in shaping the distribution and existence of quantum states, establishing a foundational cornerstone for advancing the study of twisted two-dimensional materials.
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Shi-Qi Hu and Sheng Meng 2023 Chinese Phys. Lett. 40 117801
Our understanding of how photons couple to different degrees of freedom in solids forms the bedrock of ultrafast physics and materials sciences. In this review, the emergent ultrafast dynamics in condensed matter at the attosecond timescale have been intensively discussed. In particular, the focus is put on recent developments of attosecond dynamics of charge, exciton, and magnetism. New concepts and indispensable role of interactions among multiple degrees of freedom in solids are highlighted. Applications of attosecond electronic metrology and future prospects toward attosecond dynamics in condensed matter are further discussed. These pioneering studies promise future development of advanced attosecond science and technology such as attosecond lasers, laser medical engineering, and ultrafast electronic devices.
Xiao-Feng Li et al 2022 Chinese Phys. Lett. 39 037301
Twisted bilayer graphene (TBG), which has drawn much attention in recent years, arises from van der Waals materials gathering each component together via van der Waals force. It is composed of two sheets of graphene rotated relatively to each other. Moiré potential, resulting from misorientation between layers, plays an essential role in determining the band structure of TBG, which directly relies on the twist angle. Once the twist angle approaches a certain critical value, flat bands will show up, indicating the suppression of kinetic energy, which significantly enhances the importance of Coulomb interaction between electrons. As a result, correlated states like correlated insulators emerge from TBG. Surprisingly, superconductivity in TBG is also reported in many experiments, which drags researchers into thinking about the underlying mechanism. Recently, the interest in the atomic reconstruction of TBG at small twist angles comes up and reinforces further understandings of properties of TBG. In addition, twisted multilayer graphene receives more and more attention, as they could likely outperform TBG although they are more difficult to handle experimentally. In this review, we mainly introduce theoretical and experimental progress on TBG. Besides the basic knowledge of TBG, we emphasize the essential role of atomic reconstruction in both experimental and theoretical investigations. The consideration of atomic reconstruction in small-twist situations can provide us with another aspect to have an insight into physical mechanism in TBG. In addition, we cover the recent hot topic, twisted multilayer graphene. While the bilayer situation can be relatively easy to resolve, multilayer situations can be really complicated, which could foster more unique and novel properties. Therefore, in the end of the review, we look forward to future development of twisted multilayer graphene.
Fei Xie et al 2021 Chinese Phys. Lett. 38 118401
Na-ion batteries (NIBs) have been attracting growing interests in recent years with the increasing demand of energy storage owing to their dependence on more abundant Na than Li. The exploration of the industrialization of NIBs is also on the march, where some challenges are still limiting its step. For instance, the relatively low initial Coulombic efficiency (ICE) of anode can cause undesired energy density loss in the full cell. In addition to the strategies from the sight of materials design that to improve the capacity and ICE of electrodes, presodiation technique is another important method to efficiently offset the irreversible capacity and enhance the energy density. Meanwhile, the slow release of the extra Na during the cycling is able to improve the cycling stability. In this review, we would like to provide a general insight of presodiation technique for high-performance NIBs. The recent research progress including the principles and strategies of presodiation will be introduced, and some remaining challenges as well as our perspectives will be discussed. This review aims to exhibit the basic knowledge of presodiation to inspire the researchers for future studies.
Zihan Qu et al 2021 Chinese Phys. Lett. 38 107801
In the last decade, perovskite solar cells (PSCs) have greatly drawn researchers' attention, with the power conversion efficiency surging from 3.8% to 25.5%. PSCs possess the merits of low cost, simple fabrication process and high performance, which could be one of the most promising photovoltaic technologies in the future. In this review, we focus on the summary of the updated progresses in single junction PSCs including efficiency, stability and large area module. Then, the important progresses in tandem solar cells are briefly discussed. A prospect into the future of the field is also included.
Pei-Wan Shi et al 2021 Chinese Phys. Lett. 38 035202
Interaction between shear Alfvén wave (SAW) and energetic particles (EPs) is one of major concerns in magnetically confined plasmas since it may lead to excitation of toroidal symmetry breaking collective instabilities, thus enhances loss of EPs and degrades plasma confinement. In the last few years, Alfvénic zoology has been constructed on HL-2A tokamak and series of EPs driven instabilities, such as toroidal Alfvén eigenmodes (TAEs), revered shear Alfvén eigenmodes (RSAEs), beta induced Alfvén eigenmodes (BAEs), Alfvénic ion temperature gradient (AITG) modes and fishbone modes, have been observed and investigated. Those Alfvénic fluctuations show frequency chirping behaviors through nonlinear wave-particle route, and contribute to generation of axisymmetric modes by nonlinear wave-wave resonance in the presence of strong tearing modes. It is proved that the plasma confinement is affected by Alfvénic activities from multiple aspects. The RSAEs resonate with thermal ions, and this results in an energy diffusive transport process while the nonlinear mode coupling between core-localized TAEs and tearing modes trigger avalanche electron heat transport events. Effective measures have been taken to control SAW fluctuations and the fishbone activities are suppressed by electron cyclotron resonance heating. Those experimental results will not only contribute to better understandings of energetic particles physics, but also provide technology bases for active control of Alfvénic modes on International Thermonuclear Experimental Reactor (ITER) and Chinese Fusion Engineering Testing Reactor (CFETR).
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Song et al
In the era of Internet of Things (IoTs), an energy-efficient ultraviolet (UV) photodetector (PD) is highly desirable considering the massive usage scenarios such as environmental sterilization, fire alarm and corona discharge monitoring. So far, the common self-powered UV PDs are mainly based on metal-semiconductor hetero-structures or p-n heterojunctions, where the limited intrinsic built-in electric field restricts further enhancement of the photoresponsivity. In this work, an extremely low-voltage field-effect UV PD is proposed using a gate-drain shorted amorphous IGZO (a-IGZO) thin film transistor (TFT) architecture. A combined investigation of the experimental measurements and technology computer-aided design (TCAD) simulations suggests that the reverse current (IR) of field-effect diode (FED) is highly related with the threshold voltage (Vth) of the parental TFT, implying an enhancement- mode TFT is preferable to fabricate the field-effect UV PD with low dark current. Driven by a low bias of -0.1 V, decent UV response has been realized including large UV/visible (R300/R550) rejection ratio (1.9×103), low dark current (1.15×10-12 A) as well as high photo-to-dark current ratio (PDCR, ~103) and responsivity (1.89 A/W). This field-effect photodiode provides a new platform to construct UV PDs with well-balanced photoresponse performance at a low bias, which is attractive for the design of large-scale smart sensor network with high energy efficiency.
Zhang et al
The discovery of ferromagnetic two-dimensional (2D) van der Waals (vdWs) materials provides an opportunity to explore intriguing physics and develop innovative spin electronic devices. However, the main challenge for practical applications of vdWs ferromagnetic crystals lies in the weak intrinsic ferromagnetism and small perpendicular magnetic anisotropy (PMA) above room temperature. Here, we report the intrinsic vdWs ferromagnetic crystal Fe3GaTe2, synthesized by the self-flux method, exhibiting a Curie temperature (TC) of 370 K, a high saturation magnetization of 33.47 emu/g, and a large PMA energy density of approximately 4.17 × 105 J/m3. Furthermore, for the first time, the magneto-optical effect has been systematically investigated in Fe3GaTe2. The doubly degenerate E2g(Γ) mode reverses the helicity of incident photons, indicating the existence of pseudoangular momentum (PAM) and chirality. Meanwhile, the non-degenerate non-chiral A1g(Γ) phonon exhibits a significant magneto-Raman effect under an external out-of-plane magnetic field. These results lay the groundwork for studying phonon chirality and magneto-optical phenomena in 2D magnetic materials, providing the feasibility for further fundamental research and application in spintronic devices.
Zhao et al
Hall effects have been the central paradigms in modern physics, materials science and practical applications, and have led to many exciting breakthroughs, including the discovery of topological Chern invariants and the revolution of metrological resistance standard. To date, the Hall effects have mainly focused on a single degree of freedom (DoF), and most of them require the breaking of spatial-inversion and/or time-reversal symmetries. Here we demonstrate a new type of Hall effect—layer-valley Hall effect—based on a combined layer-valley DoF characterized by the product of layer and valley indices. The layer-valley Hall effect has a quantum origin arising from the layer-valley contrasting Berry curvature, and can occur in nonmagnetic centrosymmetric crystals with both spatial-inversion and time-reversal symmetries, transcending the symmetry constraints of single DoF Hall effect based on the constituent layer or valley index. Moreover, the layer-valley Hall effect is highly tunable and shows a 'W' pattern in response to the out-of-plane electric fields. Additionally, we discuss the potential detection approaches and material-specific design principles of layer-valley Hall effect. Our results demonstrate novel Hall physics and open up exotic paradigms for new research direction of layer-valleytronics that exploits the quantum nature of the coupled layer-valley DoF.
Liu et al
The study enriched the high-pressure phase diagram of Pr-N compound by proposing five stable structures (Pnma-PrN, I4/mmm-PrN2, C2/m-PrN3, P\overline{1}-PrN4, and R3-PrN8) and two metastable structures (P\overline{1}-PrN6 and P\overline{1}-PrN10). The P\overline{1}-PrN6 with the N14-ring layer and R3-PrN8 with the N18-ring layer can be quenched to ambient conditions. For the P\overline{1}-PrN10, the N22-ring layer structure transfers into infinite chains with the pressure quenched to ambient pressure. Remarkably, a novel polynitrogen hR8-N designed by the excision of Pr atoms from R3-PrN8 is obtained and can be quenched to ambient conditions. The N-rich structures of P\overline{1}-PrN6, R3-PrN8, c-PrN10 and the solid pure nitrogen structure exhibit outstanding properties of energy density and explosive performance.
Li et al
Controlling the size and distribution of potential barriers within a medium of interacting particles can unveil unique collective behaviors and innovative functionalities. In this study, we introduce a unique superconducting hybrid device using a novel artificial spin ice structure composed of asymmetric nanomagnets. This structure forms a distinctive superconducting pinning potential that steers unconventional motion of superconducting vortices, thereby inducing a magnetic nonreciprocal effect, in contrast to the electric nonreciprocal effect commonly observed in superconducting diodes. Furthermore, the polarity of the magnetic nonreciprocity is in-situ reversible through the tunable magnetic patterns of artificial spin ice. Our findings demonstrate that artificial spin ice not only precisely modulates superconducting characteristics but also opens the door to novel functionalities, offering a groundbreaking paradigm for superconducting electronics.