查看更多>>摘要：Two-dimensional(2D)ferroelectric materials,which possess electrically switchable spontaneous polarization and can be easily integrated with semiconductor technologies,is of utmost importance in the advancement of high-integration low-power nanoelectronics.Despite the experimental discovery of certain 2D ferroelectric materials such as CuInP2S6 and In2Se3,achieving stable ferroelectricity at room temperature in these materials continues to present a significant challenge.Herein,stable ferroelectric order at room temperature in the 2D limit is demonstrated in van der Waals SnP2S6 atom layers,which can be fabricated via mechanical exfolia-tion of bulk SnP2S6 crystals.Switchable polarization is observed in thin SnP2S6 of～7 nm.Importantly,a van der Waals ferroelectric field-effect transistor(Fe-FET)with ferroelectric SnP2S6 as top-gate insulator and p-type WTe0.6Se1.4 as the channel was designed and fabricated successfully,which exhibits a clear clockwise hysteresis loop in transfer characteristics,demonstrating ferroelectric properties of SnP2S6 atomic layers.In addition,a multilayer graphene/SnP2S6/multilayer graphene van der Waals vertical heterostructure phototransistor was also fabricated successfully,exhibit-ing improved optoelectronic performances with a responsivity(R)of 2.9 A/W and a detectivity(D)of 1.4 × 1012 Jones.Our results show that SnP2S6 is a promising 2D ferroelectric material for ferroelectric-integrated low-power 2D devices.
查看更多>>摘要：Currently,magnetic storage devices are encountering the problem of achieving lightweight and high integration in mobile computing devices during the information age.As a result,there is a growing urgency for two-dimensional half-metallic materials with a high Curie temperature(TC).This study presents a theoretical investigation of the fundamental electro-magnetic properties of the monolayer hexagonal lattice ofMn2X3(X=S,Se,Te).Additionally,the potential application of Mn2X3 as magneto-resis-tive components is explored.All three of them fall into the category of ferromagnetic half-metals.In particular,the Monte Carlo simulations indi-cate that the Tc of Mn2S3 reachs 381 K,noticeably greater than room temperature.These findings present notable advantages for the application of Mn2S3 in spintronic devices.Hence,a prominent spin filtering effect is apparent when employing non-equilibrium Green's function simulations to examine the transport parameters.The resulting current magnitude is approximately 2 × 104 nA,while the peak gigantic magnetoresistance exhibits a substantial value of 8.36 × 1016％.It is noteworthy that the device demonstrates a substantial spin Seebeck effect when the tempera-ture differential between the electrodes is modified.In brief,Mn2X3 exhibits outstanding features as a high Tc half-metal,exhibiting exceptional capabilities in electrical and thermal drives spin transport.Therefore,it holds great potential for usage in spintronics applications.
查看更多>>摘要：Two-dimensional materials with high-temperature ferromagnetism and half-metallicity have the latest applications in spintronic devices.Based on first-principles calculations,we have investigated a novel two-dimensional CrS2 phase with an orthorhombic lattice.Our results suggest that it is stable in dynamics,thermodynamics,and mechanics.The ground state of monolayer orthorhombic CrS2 is both ferromagnetic and half-metallic,with a high Curie temperature of 895 K and a large spin-flipping gap on values of 0.804 eV.This room-temperature ferromagnetism and half-metallicity can maintain stability against a strong biaxial strain ranging from-5％to 5％.Meanwhile,increasing strain can significantly maintain the out-of-plane magnetic anisotropy.A density of states analysis,together with the orbital-resolved magnetic anisotropy energy,has revealed that the strain-enhanced MAE is highly related to the 3d-orbital splitting of Cr atoms.Our results suggest the monolayer orthorhombic CrS2 is an ideal candidate for future spintronics.
查看更多>>摘要：Heterostructures composed of two-dimensional van der Waals(vdW)materials allow highly controllable stacking,where interlayer twist angles introduce a continuous degree of freedom to alter the electronic band structures and excitonic physics.Motivated by the discovery of Mott insulating states and superconductivity in magic-angle bilayer graphene,the emerging research fields of"twistron-ics"and moiré physics have aroused great academic interests in the engineering of optoelectronic properties and the exploration of new quantum phenomena,in which moiré superlattice provides a pathway for the realization of artificial excitonic crystals.Here we systematically summarize the current achievements in twistronics and moiré excitonic physics,with emphasis on the roles of lattice rotational mismatches and atomic registries.Firstly,we review the effects of the interlayer twist on electronic and photonic physics,particularly on exciton properties such as dipole moment and spin-valley polarization,through interlayer interactions and electronic band structures.We also discuss the exciton dynamics in vdW heterostructures with different twist angles,like formation,transport and relaxation processes,whose mechanisms are complicated and still need further investigations.Subsequently,we review the theoretical analysis and experimental observations of moiré superlattice and moiré modulated excitons.Various exotic moiré effects are also shown,including periodic potential,moiré miniband,and varying wave function symmetry,which result in exciton localiza-tion,emergent exciton peaks and spatially alternating optical selection rule.We further introduce the expanded properties of moiré systems with external modulation factors such as electric field,doping and strain,showing that moiré lattice is a promising platform with high tunability for optoelectronic applications and in-depth study on frontier physics.Lastly,we focus on the rapidly developing field of correlated electron physics based on the moiré system,which is potentially related to the emerging quantum phenomena.
查看更多>>摘要：The study of macro continuous flow has a long history.Simultaneously,the exploration of heat and mass transfer in small systems with a particle number of several hundred or less has gained significant interest in the fields of statistical physics and nonlinear science.However,due to absence of suitable methods,the understanding of mesoscale behavior situated between the aforementioned two scenarios,which challenges the physical function of traditional continuous fluid theory and exceeds the simulation capability of microscopic molecular dynamics method,remains consider-ably deficient.This greatly restricts the evaluation of effects of mesoscale behavior and impedes the development of corresponding regulation tech-niques.To access the mesoscale behaviors,there are two ways:from large to small and from small to large.Given the necessity to interface with the prevailing macroscopic continuous modeling currently used in the mechanical engineering community,our study of mesoscale behavior begins from the side closer to the macroscopic continuum,that is from large to small.Focusing on some fundamental challenges encountered in modeling and analysis of near-continuous flows,we review the research progress of discrete Boltzmann method(DBM).The ideas and schemes of DBM in coarse-grained modeling and complex physical field analysis are introduced.The relationships,particularly the differences,between DBM and traditional fluid modeling as well as other kinetic methods are discussed.After verification and validation of the method,some applied researches including the development of various physical functions associ-ated with discrete and non-equilibrium effects are illustrated.Future directions of DBM related studies are indicated.
查看更多>>摘要：We experimentally demonstrate the generation of customized Laguerre-Gaussian(LG)beams whose intensity maxima are localized around any desired curves.The principle is to act with appropriate algebraic functions on the angular spectra of LG beams.We characterize the propagation properties of these beams and compare them with non-diffraction caustic beams possessing the same intensity profiles.The results manifest that the customized-LG beams can maintain their profiles during propagation and suffer less energy loss than the non-diffraction caustic beams,and hence are able to propagate a longer distance.Moreover,the customized-LG beam exhibits self-healing ability when parts of their bodies are blocked.This new structure beam has potential applications in areas such as optical communication,soliton routing and steering,and optical tweezing.
查看更多>>摘要：Laser-induced breakdown spectroscopy(LIBS)is regarded as the future superstar for analytical chemistry and widely applied in various fields.Improving the quality of LIBS signal is fundamental to achieving accurate quantification and large-scale commercialization of LIBS.To propose control methods that improve LIBS signal quality,it is essential to have a comprehensive understanding of the influence of key parameters,such as ambient gas pressure,temperature,and sample temperature on LIBS signals.To date,extensive research has been carried out.However,different researchers often yield significantly different experimental results for LIBS,preventing the formation of consistent conclusions.This greatly prevents the understanding of influencing laws of key parameters and the improvement of LIBS quantitative performance.Taking ambient gas pres-sure as an example,this paper compares the effects of ambient gas pressure under different optimization conditions,reveals the influence of spatiotemporal window caused by inherent characteristics of LIBS signal sources,i.e.,intense temporal changes and spatial non-uniformity of laser-induced plasmas,on the impact patterns of key parameters.From the perspective of plasma spatiotemporal evolution,the paper elucidates the influence patterns of ambient gas pressure on LIBS signals,clarifying seemingly contradictory research results in the literature.
查看更多>>摘要：Vortex wave and plane wave,as two most fundamental forms of wave propagation,are widely applied in various research fields.However,there is currently a lack of basic mechanism to enable arbitrary conversion between them.In this paper,we propose a new paradigm of extremely anisotropic acoustic metasurface(AM)to achieve the efficient conversion from 2D vortex waves with arbitrary orbital angular momentum(OAM)to plane waves.The underlying physics of this conversion process is ensured by the symmetry shift of AM medium parameters and the directional compensation of phase.Moreover,this novel phenomenon is further veri-fied by analytical calculations,numerical demonstrations,and acoustic experiments,and the deflection angle and direction of the converted plane waves are qualitatively and quantitatively confirmed by a simple formula.Our work provides new possibilities for arbitrary manipulation of acoustic vortex,and holds potential applications in acoustic communication and OAM-based devices.
查看更多>>摘要：Periodic structures structured as photonic crystals and optical lattices are fascinating for nonlinear waves engineering in the optics and ultracold atoms communities.Moiré photonic and optical lattices—two-dimen-sional twisted patterns lie somewhere in between perfect periodic struc-tures and aperiodic ones—are a new emerging investigative tool for studying nonlinear localized waves of diverse types.Herein,a theory of two-dimensional spatial localization in nonlinear periodic systems with fractional-order diffraction(linear nonlocality)and moiré optical lattices is investigated.Specifically,the flat-band feature is well preserved in shallow moiré optical lattices which,interact with the defocusing nonlinearity of the media,can support fundamental gap solitons,bound states composed of several fundamental solitons,and topological states(gap vortices)with vortex charge s=1 and 2,all populated inside the finite gaps of the linear Bloch-wave spectrum.Employing the linear-stability analysis and direct perturbed simulations,the stability and instability properties of all the localized gap modes are surveyed,highlighting a wide stability region within the first gap and a limited one(to the central part)for the third gap.The findings enable insightful studies of highly localized gap modes in linear nonlocality(fractional)physical systems with shallow moiré patterns that exhibit extremely flat bands.
查看更多>>摘要：Solving non-Hermitian quantum many-body systems on a quantum computer by minimizing the variational energy is challenging as the energy can be complex.Here,we propose a variational quantum algorithm for solving the non-Hermitian Hamiltonian by minimizing a type of energy variance,where zero variance can naturally determine the eigen-values and the associated left and right eigenstates.Moreover,the energy is set as a parameter in the cost function and can be tuned to scan the whole spectrum efficiently by using a two-step optimization scheme.Through numerical simulations,we demonstrate the algorithm for prepar-ing the left and right eigenstates,verifying the biorthogonal relations,as well as evaluating the observables.We also investigate the impact of quan-tum noise on our algorithm and show that its performance can be largely improved using error mitigation techniques.Therefore,our work suggests an avenue for solving non-Hermitian quantum many-body systems with variational quantum algorithms on near-term noisy quantum computers.
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