查看更多>>摘要：Valley-polarized quantum anomalous Hall effect(VQAHE),combined nontrivial band topology with valleytronics,is of importance for both fundamental sciences and emerging applications.However,the experimental realization of this property is challenging.Here,by using first-principles calculations and modal analysis,we predict a mechanism of pro-ducing VQAHE in two-dimensional ferromagnetic van der Waals germanene/MnI2 heterostructure.This heterostructure exhibits both valley anomalous Hall effect and VQAHE due to the joint effects of magnetic exchange effect and spin-orbital coupling with the aid of anomalous Hall conductance and chiral edge state.Moreover interestingly,through the electrical modulation of ferroelectric polarization state in In2Se3,the germanene/MnI2/In2Se3 heterostructure can undergo reversible switching from a semiconductor to a metallic behavior.This work offers a guiding advancement for searching for VQAHE in ferromagnetic van der Waals heterostructures and exploiting energy-efficient devices based on the VQAHE.
查看更多>>摘要：The kagome superconductor CsV3Sb5 has attracted widespread attention due to its rich correlated electron states in-cluding superconductivity,charge density wave(CDW),nematicity,and pair density wave.Notably,the modulation of the intertwined electronic orders by the chemical doping is significant to illuminate the cooperation/competition between multi-ple phases in kagome superconductors.In this study,we have synthesized a series of tantalum-substituted Cs(V1-xTax)3Sb5 by a modified self-flux method.Electrical transport measurements reveal that CDW is suppressed gradually and becomes undetectable as the doping content of x is over 0.07.Concurrently,the superconductivity is enhanced monotonically from Tc～2.8 K at x=0 to 5.2 K at x=0.12.Intriguingly,in the absence of CDW,Cs(V1-xTax)3Sb5(x=0.12)crystals exhibit a pronounced two-fold symmetry of the in-plane angular-dependent magnetoresistance(AMR)in the superconduct-ing state,indicating the anisotropic superconducting properties in the Cs(V1-xTax)3Sb5.Our findings demonstrate that Cs(V1-xTax)3Sb5 with the non-trivial band topology is an excellent platform to explore the superconductivity mechanism and intertwined electronic orders in quantum materials.
查看更多>>摘要：A study of single-electron capture(SEC)in 18-240 keV O6+-Ne collisions has been conducted employing a combi-nation of experimental and theoretical methodologies.Utilizing a reaction microscope,state-selective SEC cross sections and projectile scattering angle distributions were obtained.The translational energy spectra for SEC reveal the prevailing capture into n=3 states of the projectile ion,with a minor contribution from n=4 states.Notably,as the projectile's energy increases,the relative contribution of SEC n=4 states increases while that of SEC n=3 states diminishes.Fur-thermore,we computed state-selective relative cross sections and angular differential cross sections employing the classical molecular Coulomb over-the-barrier model(MCBM)and the multichannel Landau-Zener(MCLZ)model.A discernible discrepancy between the state-selective cross sections from the two theoretical models is apparent for the considered impact energies.However,regarding the angular differential cross sections,an overall agreement was attained between the current experimental results and the theoretical results from the MCLZ model.
查看更多>>摘要：This article proposes a new physics package to enhance the frequency stability of the space cold atom clock with the advantages of a microgravity environment.Clock working processes,including atom cooling,atomic state preparation,microwave interrogation,and transition probability detection,are integrated into the cylindrical microwave cavity to achieve a high-performance and compact physics package for the space cold atom clock.We present the detailed design and ground-test results of the cold atom clock physics package in this article,which demonstrates a frequency stability of 1.2 × 10-12 τ-1/2 with a Ramsey linewidth of 12.5 Hz,and a better performance is predicted with a 1 Hz or a narrower Ramsey linewidth in microgravity environment.The miniaturized cold atom clock based on intracavity cooling has great potential for achieving space high-precision time-frequency reference in the future.
查看更多>>摘要：We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments.Breakthroughs have been made in some key technologies and components of heat switches and dilution units.Our prototype has been running continuously and stably for more than 100 hours below 10 mK,with a minimum temperature of 7.6 mK and a cooling power of 450 μW at 100 mK.At the same time,we have also made progress in the application of dilution refrigerators,such as quantum computing,low-temperature detector,and magnet integration.These indicators and test results indicate good prospects for application in physics,astronomy,and quantum information.
查看更多>>摘要：FL-Online(http://fanlab.ac.cn)is an out-of-box modern web service featuring a user-friendly interface and simplified parameters,providing academic users with access to a series of online programs for biomolecular crystallography,including SAPI-online,OASIS-online,C-IPCAS-online and a series of upcoming software releases.Meanwhile,it is a highly scalable and maintainable web application framework that provides a powerful and flexible solution for academic web development needs.All the codes are open-source under MIT licenses in GitHub.
查看更多>>摘要：Metal-organic frameworks(MOFs)are crystalline porous materials with tunable properties,exhibiting great potential in gas adsorption,separation and catalysis.[1,2]It is challenging to visualize MOFs with transmission electron microscopy(TEM)due to their inherent instability under electron beam irradiation.Here,we employ cryo-electron microscopy(cryo-EM)to capture images of MOF ZIF-8,revealing inverted-space structural information at a resolution of up to about 1.7 Å and enhancing its critical electron dose to around 20 e-/Å2.In addition,it is confirmed by electron-beam irradiation experiments that the high voltage could effectively mitigate the radiolysis,and the structure of ZIF-8 is more stable along the[100]direction under electron beam irradiation.Meanwhile,since the high-resolution electron microscope images are modulated by contrast transfer function(CTF)and it is difficult to determine the positions corresponding to the atomic columns directly from the images.We employ image deconvolution to eliminate the impact of CTF and obtain the structural images of ZIF-8.As a result,the heavy atom Zn and the organic imidazole ring within the organic framework can be distinguished from structural images.
查看更多>>摘要：The REAgSb2(RE=rare earth and Y)family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties.We report herein the magnetization and magnetotransport measurements of SmAgSb2 single crystal,which unveil very large magnetoresistance and high carrier mobility up to 6.2 × 103％and 5.58 × 103 cm2·V-1·s-1,respectively.The analysis of both Shubnikov-de Haas and de Haas-van Alphen quantum oscillations indicates nontrivial Berry phases in the paramagnetic state while trivial Berry curvature in the antiferromagnetic state,indicating a topological phase transition induced by the antiferromagnetic order.It is also supported by the first-principles calculations.The results not only provide a new interesting topological material but also offer valuable insights into the correlation between magnetism and nontrivial topological states.
查看更多>>摘要：Ru-based superconductor LaRu2As2 has been discovered exhibiting the highest critical temperature of～7.8 K among iron-free transition metal pnictides with the ThCr2Si2-type crystal structure.However,microscopic research on this novel superconducting material is still lacking.Here,we utilize scanning tunneling microscopy/spectroscopy to uncover the superconductivity and surface structure of LaRu2As2.Two distinct terminating surfaces are identified on the cleaved crystals,namely,the As surface and the La surface.Atomic missing line defects are observed on the La surface.Both surfaces exhibit a superconducting gap of～1.0 meV.By employing quasiparticle interference techniques,we observe standing wave patterns near the line defects on the La atomic plane.These patterns are attributed to quasiparticle scattering from two electron type parabolic bands.
查看更多>>摘要：The stability of superconductivity in superconductors is widely recognized to be determined by various factors,includ-ing charge,spin,orbit,lattice,and other related degrees of freedom.Here,we report our findings on the pressure-induced coevolution of superconductivity and Hall coefficient in KCa2Fe4As4F2,an iron-based superconductor possessing a hybrid crystal structure combining KFe2As2 and CaFeAsF.Our investigation,involving high-pressure resistance,Hall effect and x-ray diffraction(XRD)measurements,allows us to observe the connection of the superconductivity and Hall coefficient with the anisotropic lattice shrinkage.We find that its ambient-pressure tetragonal(T)phase presents a collapse starting at around 18 GPa,where the sign of the Hall coefficient(RH)changes from positive to negative.Upon further compression,both superconducting transition temperature(Tc)and RH exhibit a monotonous decrease.At around 41 GPa,the supercon-ductivity is completely suppressed(Tc=0),where the parameter a begins to decline again and the Hall coefficient remains nearly unchanged.Our experiment results clearly demonstrate that the pressure-induced anisotropic lattice collapse plays a crucial role in tuning the interplay among multiple degrees of freedom in the superconducting system and,correspondingly,the stability of the superconductivity.
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