查看更多>>摘要：Kinetically constrained spin systems are toy models of supercooled liquids and amorphous solids.In this perspective,we revisit the prototypical Fredrickson-Andersen(FA)kinetically constrained model from the viewpoint of K-core combi-natorial optimization.Each kinetic cluster of the FA system,containing all the mutually visitable microscopic occupation configurations,is exactly the solution space of a specific instance of the K-core attack problem.The whole set of different jammed occupation patterns of the FA system is the configuration space of an equilibrium K-core problem.Based on recent theoretical results achieved on the K-core attack and equilibrium K-core problems,we discuss the thermodynamic spin glass phase transitions and the maximum occupation density of the fully unfrozen FA kinetic cluster,and the minimum occupation density and extreme vulnerability of the partially frozen(jammed)kinetic clusters.The equivalence between K-core attack and the fully unfrozen FA kinetic cluster also implies a new way of sampling K-core attack solutions.
查看更多>>摘要：Aerogel nanoporous materials possess high porosity,high specific surface area,and extremely low density due to their unique nanoscale network structure.Moreover,their effective thermal conductivity is very low,making them a new type of lightweight and highly efficient nanoscale super-insulating material.However,prediction of their effective thermal conductivity is challenging due to their uneven pore size distribution.To investigate the internal heat transfer mechanism of aerogel nanoporous materials,this study constructed a cross-aligned and cubic pore model(CACPM)based on the actual pore arrangement of SiO2 aerogel.Based on the established CACPM,the effective thermal conductivity expression for the aerogel was derived by simultaneously considering gas-phase heat conduction,solid-phase heat conduction,and radiative heat transfer.The derived expression was then compared with available experimental data and the Wei structure model.The results indicate that,according to the model established in this study for the derived thermal conductivity formula of silica aerogel,for powdery silica aerogel under the conditions of T=298 K,a2=0.85,D1=90 μm,ρ=128 kg/m3,within the pressure range of 0-105 Pa,the average deviation between the calculated values and experimental values is 10.51％.In the pressure range of 103-104 Pa,the deviation between calculated values and experimental values is within 4％.Under these conditions,the model has certain reference value in engineering verification.This study also makes a certain contribution to the research of aerogel thermal conductivity heat transfer models and calculation formulae.
查看更多>>摘要：Based on previously reported work,we propose a new method for calibrating image plate(IP)scanners,offering greater flexibility and convenience,which can be extended to the calibration tasks of various scanner models.This method was applied to calibrate the sensitivity of a GE Typhoon FLA 7000 scanner.Additionally,we performed a calibration of the spontaneous signal attenuation behavior for BAS-MS,BAS-SR,and BAS-TR type IPs under the 20±1 ℃ environmental conditions,and observed significant signal carrier diffusion behavior in BAS-MS IP.The calibration results lay a foundation for further research on the interaction between ultra-short,ultra-intense lasers and matter.
查看更多>>摘要：How to control the dynamic behavior of large-scale artificial active matter is a critical concern in experimental research on soft matter,particularly regarding the emergence of collective behaviors and the formation of group patterns.Centralized systems excel in precise control over individual behavior within a group,ensuring high accuracy and controllability in task execution.Nevertheless,their sensitivity to group size may limit their adaptability to diverse tasks.In contrast,decentralized systems empower individuals with autonomous decision-making,enhancing adaptability and system robustness.Yet,this flexibility comes at the cost of reduced accuracy and efficiency in task execution.In this work,we present a unique method for regulating the centralized dynamic behavior of self-organizing clusters based on environmental interactions.Within this environment-coupled robot system,each robot possesses similar dynamic characteristics,and their internal programs are entirely identical.However,their behaviors can be guided by the centralized control of the environment,facilitating the accomplishment of diverse cluster tasks.This approach aims to balance the accuracy and flexibility of centralized control with the robustness and task adaptability of decentralized control.The proactive regulation of dynamic behavioral characteristics in active matter groups,demonstrated in this work through environmental interactions,holds the potential to introduce a novel technological approach and provide experimental references for studying the dynamic behavior control of large-scale artificial active matter systems.
查看更多>>摘要：Mechanical strain can induce noteworthy structural and electronic changes in vanadium dioxide,imparting substantial scientific importance to both the exploration of phase transitions and the development of potential technological applica-tions.Unlike the traditional rutile(R)phase,bronze-phase vanadium dioxide[VO2(B)]exhibits an in-plane anisotropic structure.When subjected to stretching along distinct crystallographic axes,VO2(B)may further manifest the axial depen-dence in lattice-electron interactions,which is beneficial for gaining insights into the anisotropy of electronic transport.Here,we report an anisotropic room-temperature metal-insulator transition in single-crystal VO2(B)by applying in-situ uniaxial tensile strain.This material exhibits significantly different electromechanical responses along two anisotropic axes.We reveal that such an anisotropic electromechanical response mainly arises from the preferential arrangement of a strain-induced unidirectional stripe state in the conductive channel.This insulating stripe state could be attributed to the in-plane dimerization within the distorted zigzag chains of vanadium atoms,evidenced by strain-modulated Raman spectra.Our work may open up a promising avenue for exploiting the anisotropy of metal-insulator transition in vanadium dioxide for potential technological applications.
查看更多>>摘要：Conventional theories expect that materials under pressure exhibit expanded valence and conduction bands,leading to increased electrical conductivity.Here,we report the electrical properties of the doped lT-TiS2 under high pressure by electrical resistance investigations,synchrotron x-ray diffraction,Raman scattering and theoretical calculations.Up to 70 GPa,an unusual metal-semiconductor-metal transition occurs.Our first-principles calculations suggest that the observed anti-Wilson transition from metal to semiconductor at 17 GPa is due to the electron localization induced by the intercalated Ti atoms.This electron localization is attributed to the strengthened coupling between the doped Ti atoms and S atoms,and the Anderson localization arising from the disordered intercalation.At pressures exceeding 30.5 GPa,the doped TiS2 undergoes a re-metallization transition initiated by a crystal structure phase transition.We assign the most probable space group as P212121.Our findings suggest that materials probably will eventually undergo the Wilson transition when subjected to sufficient pressure.
查看更多>>摘要：Unraveling the mechanism underlying topological phases,notably the Chem insulators(ChIs)in strong correlated systems at the microscopy scale,has captivated significant research interest.Nonetheless,ChIs harboring topological information have not always manifested themselves,owing to the constraints imposed by displacement fields in certain ex-perimental configurations.In this study,we employ density-tuned scanning tunneling microscopy(DT-STM)to investigate the ChIs in twisted monolayer-bilayer graphene(tMBG).At zero magnetic field,we observe correlated metallic states.While under a magnetic field,a metal-insulator transition happens and an integer ChI is formed emanating from the filling index s=3 with a Chem number C=1.Our results underscore the pivotal role of magnetic fields as a powerful probe for elucidating topological phases in twisted Van der Waals heterostructures.
查看更多>>摘要：Band structure analysis holds significant importance for understanding the optoelectronic characteristics of semicon-ductor structures and exploring their potential applications in practice.For quantum well structures,the energy of carriers in the well splits into discrete energy levels due to the confinement of barriers in the growth direction.However,the discrete energy levels obtained at a fixed wave vector cannot accurately reflect the actual energy band structure.In this work,the band structure of the type-Ⅱ quantum wells is reanalyzed.When the wave vectors of the entire Brillouin region(corre-sponding to the growth direction)are taken into account,the quantized energy levels of the carriers in the well are replaced by subbands with certain energy distributions.This new understanding of the energy bands of low-dimensional structures not only helps us to have a deeper cognition of the structure,but also may overturn many viewpoints in traditional band theories and serve as supplementary to the band theory of low-dimensional systems.
查看更多>>摘要：We revisited the vortex states of 2H-NbSe2 towards zero fields by a low-temperature scanning tunneling microscope.Fine structures of the anisotropic vortex states were distinguished,one is a spatially non-splitting zero bias peak,and the other is an in-gap conductance anomaly resembling evolved crossing features around the center of the three nearest vortices.Both of them distribute solely along the next nearest neighboring direction of the vortex lattice and become unresolved in much higher magnetic fields,implying an important role played by the vortex-vortex interactions.To clarify these issues,we have studied the intrinsic vortex states of the isolated trapped vortex in zero fields at 0.45 K.It is concluded that the anisotropic zero bias peak is attributed to the superconducting gap anisotropy,and the spatially evolved crossing features are related to the vortex-vortex interaction.The vortex core size under the zero-field limit is determined.These results provide a paradigm for studying the inherent vortex states of type-Ⅱ superconductors especially based on an isolated vortex.
查看更多>>摘要：Manipulating emergent quantum phenomena is a key issue for understanding the underlying physics and contributing to possible applications.Here we study the evolution of insulating ground states of Ta2Pd3Te5 and Ta2Ni3Te5 under in-situ surface potassium deposition via angle-resolved photoemission spectroscopy.Our results confirm the excitonic insulator character of Ta2Pd3Te5.Upon surface doping,the size of its global gap decreases obviously.After a deposition time of more than 7 min,the potassium atoms induce a metal-insulator phase transition and make the system recover to a normal state.In contrast,our results show that the isostructural compound Ta2Ni3Te5 is a conventional insulator.The size of its global gap decreases upon surface doping,but persists positive throughout the doping process.Our results not only confirm the excitonic origin of the band gap in Ta2Pd3Te5,but also offer an effective method for designing functional quantum devices in the future.
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