查看更多>>摘要：A simple semi-analytical collective model that takes into account the limitations of the variation interval of the collective variable is suggested to describe the chiral dynamics in triaxial odd-odd nuclei with a fixed particle-hole configuration.The collective Hamiltonian is constructed with the potential energy obtained using the postulated ansatz for the wave func-tion symmetric with respect to chiral transformation.By diagonalizing the collective Hamiltonian the wave functions of the lowest states are obtained and the evolution of the energy splitting of the chiral doublets in transition from chiral vibration to chiral rotation regime is demonstrated.
查看更多>>摘要：Progress in the studies of chirality in atomic nuclei at iThemba LABS is reviewed.New regions of chirality,around mass 80 and 190 have been discovered using the AFRODITE array,specifically in the nuclei 74As,78,80,82Br,81Kr,and 193,194,198Tl.Many phenomena have been observed,including multiple chiral bands in the same nucleus,the coexistence of octupole correlations and nuclear chirality,and the coexistence of pseudo spin and nuclear chirality.The best example of chiral degeneracy to date was found in 194Tl.The level scheme of 106Ag has been revisited and inter-preted in terms of two-and four-quasiparticle bands.Investigations using the particle-rotor model have shown that the fingerprints of chirality in the two-quasiparticle system only can occur in an idealised model descrip-tion.For systems with a higher number of quasiparticles,the calculations showed that nuclear chirality can persist.
查看更多>>摘要：The application of the semiclassical description to a particle-core system with imbued chiral symmetry is presented.The classical features of the chiral geometry in atomic nuclei and the associated dynamics are investi-gated for various core deformations and single-particle alignments.Distinct dynamical characteristics are identified in specific angular momentum ranges,triaxiality and alignment conditions.Quantum observ-ables will be extracted from the classical picture for a quantitative descrip-tion of experimental data provided as numerical examples of the model's performance.
查看更多>>摘要：Quasi-two-dimensional(2D)Ruddlesden-Popper(RP)halide perovskites,as a kind of emerged two-dimensional layered materials,have recently achieved great attentions in lasing materials field owing to their large exci-ton binding energy,high emission yield,large optical gain,and wide-range tuning of optical bandgap.This review will introduce research progresses of RP halide perovskites for lasing applications in aspects of materials,photophysics,and devices with emphasis on emission and lasing properties tailored by the molecular composition and interface.The materials,struc-tures and fabrications are introduced in the first part.Next,the optical transitions and amplified spontaneous emission properties are discussed from the aspects of electronic structure,exciton,gain dynamics,and inter-face tailoring.Then,the research progresses on lasing devices are summa-rized and several types of lasers including VCSEL,DFB lasers,microlasers,random lasers,plasmonic lasers,and polariton lasers are discussed.At last,the challenges and perspectives would be provided.
查看更多>>摘要：With the emergence of the Internet of Things(IoT)and the rapid growth of big data generated by edge devices,there has been a growing need for electronic devices that are capable of processing and transmitting data at low power and high speeds.Traditional Complementary Metal-Oxide-Semiconductor(CMOS)devices are nonvolatile and often limited by their ability for certain IoT applications due to their unnecessary power consumption for data movement in von Neuman architecture-based systems.This has led to a surge in research and development efforts aimed at creating innovative electronic components and systems that can over-come these shortcomings and meet the evolving needs of the information era,which share features such as improved energy efficiency,higher processing speeds,and increased functionality.Memristors are a novel type of electronic device that has the potential to break down the barrier between storage and computing.By storing data and processing informa-tion within the same device,memristors can minimize the need for data movement,which allows for faster processing speeds and reduced energy consumption.To further improve the energy efficiency and reliability of memristors,there has been a growing trend toward diversifying the selec-tion of dielectric materials used in memristors.Halide perovskites(HPs)have unique electrical and optical properties,including ion migration,charge trapping effect caused by intrinsic defects,excellent optical absorp-tion efficiency,and high charge mobility,which makes them highly promising in applications of memristors.In this paper,we provide a comprehensive overview of the recent development in resistive switching behaviors of HPs and the underlying mechanisms.Furthermore,we summarize the diverse range of HPs,their respective performance metrics,as well as their applications in various fields.Finally,we critically evaluate the current bottlenecks and possible opportunities in the future research of HP memristors.
查看更多>>摘要：Two-dimensional transition metal dichalcogenides(TMDs)exhibit promising application prospects in the domains of electronic devices,optoelectronic devices and spintronic devices due to their distinctive energy band structures and spin-orbit coupling properties.Cr-based chalcogenides with narrow or even zero bandgap,covering from semicon-ductors to metallic materials,have considerable potential for wide-band photodetection and two-dimensional magnetism.Currently,the prepara-tion of 2D CrXn(X=S,Se,Te)nanosheets primarily relies on chemical vapor deposition(CVD)and molecule beam epitaxy(MBE),which enable the production of high-quality large-area materials.This review article focuses on recent progress of 2D Cr-based chalcogenides,including unique crystal structure of the CrXn system,phase-controlled synthesis,and heterojunction construction.Furthermore,a detailed introduction of room-temperature ferromagnetism and electrical/optoelectronic properties of 2D CrXn is presented.Ultimately,this paper summarizes the challenges associated with utilizing 2D Cr-based chalcogenides in preparation strate-gies,optoelectronics devices,and spintronic devices while providing further insights.
查看更多>>摘要：Valleytronic materials can provide new degrees of freedom to future elec-tronic devices.In this work,the concepts of the ferrovalley metal(FVM)and valley gapless semiconductor(VGS)are proposed,which can be achieved in valleytronic bilayer systems by electric field engineering.In valleytronic bilayer systems,the interaction between out-of-plane ferro-electricity and A-type antiferromagnetism can induce layer-polarized anomalous valley Hall(LP-AVH)effect.The K and-K valleys of FVM are both metallic,and electron and hole carriers simultaneously exist.In the extreme case,the FVM can become VGS by analogizing spin gapless semi-conductor(SGS).Moreover,it is proposed that the valley splitting enhancement and valley polarization reversal can be achieved by electric field engineering in valleytronic bilayer systems.Taking the bilayer RuBr2 as an example,our proposal is confirmed by the first-principle calculations.The FVM and VGS can be achieved in bilayer RuBr2 by applying electric field.With appropriate electric field range,increasing electric field can enhance valley splitting,and the valley polarization can be reversed by flipping electric field direction.To effectively tune valley properties by electric field in bilayer systems,the parent monolayer should possess out-of-plane magnetization,and have large valley splitting.Our results shed light on the possible role of electric field in tuning valleytronic bilayer systems,and provide a way to design the ferrovalley-related material by electric field.
查看更多>>摘要：Exciton physics in atomically thin transition-metal dichalcogenides(TMDCs)holds paramount importance for fundamental physics research and prospective applications.However,the experimental exploration of exciton physics,including excitonic coherence dynamics,exciton many-body interactions,and their optical properties,faces challenges stemming from factors such as spatial heterogeneity and intricate many-body effects.In this perspective,we elaborate upon how optical two-dimensional coher-ent spectroscopy(2DCS)emerges as an effective tool to tackle the chal-lenges,and outline potential directions for gaining deeper insights into exciton physics in forthcoming experiments with the advancements in 2DCS techniques and new materials.
查看更多>>摘要：Recent studies have shown that the construction of nanophononic meta-materials can reduce thermal conductivity without affecting electrical properties,making them promising in many fields of application,such as energy conversion and thermal management.However,although extensive studies have been carried out on thermal conductivity reduction in nanophononic metamaterials,the local heat flux characteristic is still unclear.In this work,we construct a heat flux regulator which includes a silicon nanofilm with silicon pillars.The regulator has remarkable heat flux regulation ability,and various impacts on the regulation ability are explored.Surprisingly,even in the region without nanopillars,the local heat current is still lower than that in pristine silicon nanofilms,reduced by the neighboring nanopillars through the thermal proximity effect.We combine the analysis of the phonon participation ratio with the intensity of localized phonon modes to provide a clear explanation.Our findings not only provide insights into the mechanisms of heat flux regulation by nanophononic metamaterials,but also will open up new research directions to control local heat flux for a broad range of applications,including heat management,thermoelectric energy conversion,thermal cloak,and ther-mal concentrator.
查看更多>>摘要：Rare-earth orthoferrite REFeO3(where RE is a rare-earth ion)is gaining interest.We created a high-entropy orthoferrite(Tm0.2Nd0.2Dy0.2Y0.2Yb0.2)FeO3(HEOR)by doping five RE ions in equimolar ratios and grew the single crystal by optical floating zone method.It strongly tends to form a single-phase structure stabilized by high configurational entropy.In the low-temperature region(11.6-14.4 K),the spin reorientation transition(SRT)of Γ2(Fx,Cy,Gz)-Γ24-Γ4(Gx,Ay,Fz)occurs.The weak ferromagnetic(FM)moment,which comes from the Fe sublattices distortion,rotates from the a-to c-axis.The two-step dynamic processes(Γ2-Γ24-Γ4)are iden-tified by AC susceptibility measurements.SRT in HEOR can be tuned in the range of 50-60000 Oe,which is an order of magnitude larger than that of orthoferrites in the peer system,making it a candidate for high-field spin sensing.Typical spin-switching(SSW)and continuous spin-switching(CSSW)effects occur under low magnetic fields due to the strong interac-tions between RE-Fe sublattices.The CSSW effect is tunable between 20-50 Oe,and hence,HEOR potentially can be applied to spin modulation devices.Furthermore,because of the strong anisotropy of magnetic entropy change(-ΔSm)and refrigeration capacity(RC)based on its high configurational entropy,HEOR is expected to provide a novel approach for refrigeration by altering the orientations of the crystallographic axes(anisotropic configurational entropy).
NETL
NSTL
万方数据