This paper presents a fringe-carrier method that eliminates sign ambiguity of transient moire fringes which can be used to automatically determine the relative orders. A fringe carrier is preset in the static state of...This paper presents a fringe-carrier method that eliminates sign ambiguity of transient moire fringes which can be used to automatically determine the relative orders. A fringe carrier is preset in the static state of the specimen and the dynamic in-plane displacements are recorded as the modulation to the frequency of the carrier fringes when the specimen is loaded by impact. According to a modulating criterion developed from the modulation degree, the fringes of the transient moire patterns keep monotonical in orders so that they can be automatically encoded in grey levels by a digital image system. The moire orders purely caused by dynamic loadings are evaluated by subtracting the grey-value of the unmodulated carrier image from that of the modulated carrier images encoded by their orders. With the subtracted moire orders the strain components can be obtained, and, correspondingly, the histograms of dynamic displacement moire images are shown with order variation by image-difference.展开更多
A new method for constructing digital-strain-field-image from a moire pattern with the help of digital image processing technique is proposed in this paper. The digital-strain-field-image expresses the strain values d...A new method for constructing digital-strain-field-image from a moire pattern with the help of digital image processing technique is proposed in this paper. The digital-strain-field-image expresses the strain values directly by its grey levels. The digital-strain-field-image can be obtained by making a differentiation for the digital moire pattern and doing a simple division operation. This image not only gives the visual strain field distribution, but also gives the strain values of every point. This method is simple and applicable and has satisfactory accuracy.展开更多
A hybrid technique of combining moire measurement and analytical solution is developed to separate the normal and the tangential components of distributed contact stresses between two co-plane bodies. The moire interf...A hybrid technique of combining moire measurement and analytical solution is developed to separate the normal and the tangential components of distributed contact stresses between two co-plane bodies. The moire interfe-rometry offers the displacement fields near the deformed contact zone, from which the tangential strains and boundary slopes of the deformed configurations can be evaluated. Those experimental results provide boundary conditions for the discrete integration of Flamant＇s solutions, to inversely compute the separated components of the contact stresses.展开更多
In moiré-patterned van der Waals structures of transition metal dichalcogenides,correlated insulators can form under integer and fractional fillings,whose transport properties are governed by various quasiparticl...In moiré-patterned van der Waals structures of transition metal dichalcogenides,correlated insulators can form under integer and fractional fillings,whose transport properties are governed by various quasiparticle excitations including holons,doublons and interlayer exciton insulators.Here we theoretically investigate the nearest-neighbor inter-site hoppings of holons and interlayer exciton insulators.Our analysis indicates that these hopping strengths are significantly enhanced compared to that of a single carrier.The underlying mechanism can be attributed to the strong Coulomb interaction between carriers at different sites.For the interlayer exciton insulator consisting of a holon and a carrier in different layers,we have also obtained its effective Bohr radius and energy splitting between the ground and the first-excited states.展开更多
We theoretically investigated the chiral phonons of honeycomb-type bilayer Wigner crystals recently discovered in van der Waals structures of layered transition metal dichalcogenides. These chiral phonons can emerge u...We theoretically investigated the chiral phonons of honeycomb-type bilayer Wigner crystals recently discovered in van der Waals structures of layered transition metal dichalcogenides. These chiral phonons can emerge under the inversion symmetry breaking introduced by an effective mass imbalance between the two layers or a moiré potential in one layer, as well as under the time-reversal symmetry breaking realized by applying a magnetic field. Considering the wide tunability of layered materials, the frequencies and chirality of phonons can both be tuned by varying the system parameters. These findings suggest that bilayer honeycomb-type Wigner crystals can serve as an exciting new platform for studying chiral phonons.展开更多
Using the Lindemann criterion,we analyzed the quantum and thermal melting of electronic/excitonic crystals recently discovered in two-dimensional(2D)semiconductor moirépatterns.We show that the finite 2D screenin...Using the Lindemann criterion,we analyzed the quantum and thermal melting of electronic/excitonic crystals recently discovered in two-dimensional(2D)semiconductor moirépatterns.We show that the finite 2D screening of the atomically thin material can suppress(enhance)the inter-site Coulomb(dipolar)interaction strength,thus inhibits(facilitates)the formation of the electronic(excitonic)crystal.Meanwhile,a strong enough moiréconfinement is found to be essential for realizing the crystal phase with a wavelength near 10 nm or shorter.From the calculated Lindemann ratio which quantifies the fluctuation of the site displacement,we estimate that the crystal will melt into a liquid above a critical temperature ranging from several tens Kelvin to above 100 K(depending on the system parameters).展开更多
Moiré patterns on HOPG were studied with scanning tunneling microscopy （STM）. The results reveal that the observed Moiré patterns originate from the defects locating several layers below the surface, which...Moiré patterns on HOPG were studied with scanning tunneling microscopy （STM）. The results reveal that the observed Moiré patterns originate from the defects locating several layers below the surface, which presents the first experimental evidence supporting the prediction that in HOPG the nanoscale electronic waves can propagate through several layers without obvious decay.展开更多
We report on the formation of a graphene monolayer on a Ru（0001） surface by annealing the Ru（0001） crystal. The samples are characterized by scanning tunnelling microscopy （STM） and Auger electron spectroscopy ...We report on the formation of a graphene monolayer on a Ru（0001） surface by annealing the Ru（0001） crystal. The samples are characterized by scanning tunnelling microscopy （STM） and Auger electron spectroscopy （AES）. STM images show that the Moire pattern is caused by the graphene layer mismatched with the underlying Ru（0001） surface and has an N × N superlattice. It is further found that the graphene monolayer on a Ru（0001） surface is very stable at high temperatures. Our results provide a simple and convenient method to produce a graphene monolayer on the Ru（0001） surface, which is used as a template for fabricating functional nanostructures needed in future nano devices and catalysis.展开更多
Sintered permanent magnetic strontium ferrites were studied using transmission electron microscopy to investigate the microstructure morphology and its correlation with the magnetic properties. The present study shows...Sintered permanent magnetic strontium ferrites were studied using transmission electron microscopy to investigate the microstructure morphology and its correlation with the magnetic properties. The present study shows that the microstructure of sintered permanent magnetic strontium ferrites is an important parameter in determining their magnetic properties. The microstructure morphology in low-performance ferrite magnet is obviously different from high-performance one. The magnetic properties of sintered permanent strontium ferrite depend strongly on the orientation degree of strong magnetic crystals. The presence of ferric oxide phase in ferrite magnet can deteriorate the magnetic properties. Moreover, proper quantities of crystal defects are beneficial to high coercive force due to the fixing of magnetic domain.展开更多
Moirépatterns in physics are interference fringes produced when a periodic template is stacked on another similar one with different displacement and twist angles.The phonon in two-dimensional(2D)material affecte...Moirépatterns in physics are interference fringes produced when a periodic template is stacked on another similar one with different displacement and twist angles.The phonon in two-dimensional(2D)material affected by moirépatterns in the lattice shows various novel physical phenomena,such as frequency shift,different linewidth,and mediation to the superconductivity.This review gives a brief overview of phonons in 2D moirésuperlattice.First,we introduce the theory of the moiréphonon modes based on a continuum approach using the elastic theory and discuss the effect of the moirépattern on phonons in 2D materials such as graphene and MoS_(2).Then,we discuss the electron-phonon coupling(EPC)modulated by moirépatterns,which can be detected by the spectroscopy methods.Furthermore,the phonon-mediated unconventional superconductivity in 2D moirésuperlattice is introduced.The theory of phonon-mediated superconductivity in moirésuperlattice sets up a general framework,which promises to predict the response of superconductivity to various perturbations,such as disorder,magnetic field,and electric displacement field.展开更多
This article considers collectively some of the most recent advances in the application of microscopicaland microanalytical techniques in materials science. including studies concerning rare metals. These comprise the...This article considers collectively some of the most recent advances in the application of microscopicaland microanalytical techniques in materials science. including studies concerning rare metals. These comprise the highest resolution obtained with electron microscopy. observation of moire patterns in transmisionelectron microscopy (TEM), electro-dimpling before ion beam thinning as an effective step in the preparation of TEM samples, hydrogen problem in atom probe analysis, and a novel analysis technique-lasermicroprobe mass spectrometry (LAMMS).展开更多
The distinct images of intragranular VC were observed on TEM in superalloy GH36 underwent normal heat treatment and prolonged aging.The size of VC particles were meas- ured by means of Moire pattern,and the misfit bet...The distinct images of intragranular VC were observed on TEM in superalloy GH36 underwent normal heat treatment and prolonged aging.The size of VC particles were meas- ured by means of Moire pattern,and the misfit between VC and austenite was also calculated. The M23C6 enveloped in VC shell was also observed in the prolonged-aged specimens.The coherent relation between intragranular M_(23)C_6 twins and austenite as well as its coherent in- terface were also studied.展开更多
Moirépatterns from two-dimensional(2D)graphene heterostructures assembled via van der Waals interactions have sparked considerable interests in physics with the purpose to tailor the electronic properties of grap...Moirépatterns from two-dimensional(2D)graphene heterostructures assembled via van der Waals interactions have sparked considerable interests in physics with the purpose to tailor the electronic properties of graphene.Here we report for the first time the observation of moire patterns arising from a bilayer graphone/graphene superlattice produced through direct single-sided hydrogenation of a bilayer graphene on substrate.Compared to pristine graphene,the bilayer superlattice exhibits a rippled surface and two types of moire patterns are observed:triangular and linear moire patterns with the periodicities of 11 nm and 8-9 nm,respectively.These moire patterns are revealed from atomic force microscopy and further confirmed by following fast Fourier transform(FFT)analysis.Density functional theory(DFT)calculations are also performed and the optimized lattice constants of bilayer superlattice heterostructure are in line with our experimental analysis.These findings show that well-defined triangular and linear periodic potentials can be introduced into the graphene system through the single-sided hydrogenation and also open a route towards the tailoring of electronic properties of graphene by various moirépotentials.展开更多
Recently,the simulation of moiréphysics using cold atom platforms has gained significant attention.These platforms provide an opportunity to explore novel aspects of moiréphysics that go beyond the limits of...Recently,the simulation of moiréphysics using cold atom platforms has gained significant attention.These platforms provide an opportunity to explore novel aspects of moiréphysics that go beyond the limits of traditional condensed matter systems.Building on recent experimental advancements in creating twisted bilayer spin-dependent optical lattices for pseudospin-1/2 Bose gases,we extend this concept to a trilayer optical lattice for spin-1 Bose gases.Unlike conventional moirépatterns,which are typically induced by interlayer tunneling or interspin coupling,the moirépattern in this trilayer system arises from inter-species atomic interactions.We investigate the ground state of Bose-Einstein condensates loaded in this spin-1 twisted optical lattice under both ferromagnetic and antiferromagnetic interactions.We find that the ground state forms a periodic pattern of distinct phases in the homogeneous case,including ferromagnetic,antiferromagnetic,polar,and broken axial symmetry phases.Additionally,by quenching the optical lattice potential strength,we examine the quench dynamics of the system above the ground state and observe the emergence of topological excitations such as vortex pairs.This study provides a pathway for exploring the rich physics of spin-1 twisted optical lattices and expands our understanding of moirésystems in synthetic quantum platforms.展开更多
Moire superlattice has recently been found in topological insulators,which can lead to periodic modulation on the electronic structure.In this work,we report the low-temperature scanning tunneling microscopy study of ...Moire superlattice has recently been found in topological insulators,which can lead to periodic modulation on the electronic structure.In this work,we report the low-temperature scanning tunneling microscopy study of Sb_(2)Te_(3) films grown on graphitized 4H-SiC.We find that substrate temperature can strongly influence the rotation angles between Sb_(2)Te_(3) film and graphene substrate.Three kinds of moire patterns are observed at the first quintuple layer Sb_(2)Te_(3) film under different substrate temperatures.One shows complicated patterns with a rotation angle of nearly 0°relative to the substrate,another just exhibits simple 1 ×1 structure with a rotation angle of 30°.Other rotation angle like 8.2°is observed at higher substrate temperature as well,which is relatively rare.Comparison of the d//dV curves from Sb_(2)Te_(3) films with different moire patterns indicates that the superstructure can offer degrees of freedom in tailoring electronic structure.This work may stimulate the further study on the moire modulation to the electronic properties of topological insulators.展开更多
Two-dimensional materials are excellent lubricants with inherent advantages.However,superlubricity has been reported for only a few of these materials.Unfortunately,other promising two-dimentional(2D)materials with di...Two-dimensional materials are excellent lubricants with inherent advantages.However,superlubricity has been reported for only a few of these materials.Unfortunately,other promising two-dimentional(2D)materials with different physical properties cannot be discovered or applied in production;thus,energy consumption can be greatly reduced.Here,we carry out high-throughput calculations for 1,4752D materials and screen for low-friction materials.To set a standard,we propose,for the first time,a geometry-independent lubricating figure of merit based on the conditions for stick-slip transition and our theory of Moiréfriction.For the efficient calculation of this figure of merit,an innovative approach was developed based on an improved registry index model.Through calculations,340 materials were found to have a figure of merit lower than 10−3.Eventually,a small set of 21 materials with a figure of merit lower than 10−4 were screened out.These materials can provide diverse choices for various applications.In addition,the efficient computational approach demonstrated in this work can be used to study other stacking-dependent properties.展开更多
Moiré interlayer exciton in transition metal dichalcogenide heterobilayer features a permanent electric dipole that enables the electrostatic control of its flow, and optical dipole that is spatially varying in t...Moiré interlayer exciton in transition metal dichalcogenide heterobilayer features a permanent electric dipole that enables the electrostatic control of its flow, and optical dipole that is spatially varying in the moiré landscape. We show the hybridization of moiré interlayer exciton with photons in a planar 2D cavity leads to two types of moiré polaritons that exhibit distinct forms of topological transport phenomena including the spin/valley Hall and polarization Hall effects, which feature remarkable electrical tunability through the control of exciton-cavity detuning by the interlayer bias.展开更多
Microscopic features of graphene segregated on Ni films prior to chemical transfer--including atomic structures of monolayers and bilayers, Moire patterns due to non-AB stacking, as well as wrinkles and ripples caused...Microscopic features of graphene segregated on Ni films prior to chemical transfer--including atomic structures of monolayers and bilayers, Moire patterns due to non-AB stacking, as well as wrinkles and ripples caused by strain effects-have been characterized in detail by high-resolution scanning tunneling microscopy （STM）. We found that the stacking geometry of the bilayer graphene usually deviates from the traditional Bernal stacking （or so-called AB stacking）, resulting in the formation of a variety of Moir6 patterns. The relative rotations inside the bilayer were then qualitatively deduced from the relationship between Moir6 patterns and carbon lattices. Moreover, we found that typical defects such as wrinkles and ripples tend to evolve around multi-step boundaries of Ni, thus reflecting strong perturbations from substrate corrugations. These investigations of the morphology and the mechanism of formation of wrinkles and ripples are fundamental topics in graphene research. This work is expected to contribute to the exploration of electronic and transport properties of wrinkles and ripples.展开更多
基金The project supported by Alexander von Humboldt Foundation or Germany and the National Natural Science Foundation of China
文摘This paper presents a fringe-carrier method that eliminates sign ambiguity of transient moire fringes which can be used to automatically determine the relative orders. A fringe carrier is preset in the static state of the specimen and the dynamic in-plane displacements are recorded as the modulation to the frequency of the carrier fringes when the specimen is loaded by impact. According to a modulating criterion developed from the modulation degree, the fringes of the transient moire patterns keep monotonical in orders so that they can be automatically encoded in grey levels by a digital image system. The moire orders purely caused by dynamic loadings are evaluated by subtracting the grey-value of the unmodulated carrier image from that of the modulated carrier images encoded by their orders. With the subtracted moire orders the strain components can be obtained, and, correspondingly, the histograms of dynamic displacement moire images are shown with order variation by image-difference.
文摘A new method for constructing digital-strain-field-image from a moire pattern with the help of digital image processing technique is proposed in this paper. The digital-strain-field-image expresses the strain values directly by its grey levels. The digital-strain-field-image can be obtained by making a differentiation for the digital moire pattern and doing a simple division operation. This image not only gives the visual strain field distribution, but also gives the strain values of every point. This method is simple and applicable and has satisfactory accuracy.
基金the National Basic Research Program(2007CB935602)the National Natural Science Foundation of China(90607004)the ICM Fund of CAEP(42105080106).
文摘A hybrid technique of combining moire measurement and analytical solution is developed to separate the normal and the tangential components of distributed contact stresses between two co-plane bodies. The moire interfe-rometry offers the displacement fields near the deformed contact zone, from which the tangential strains and boundary slopes of the deformed configurations can be evaluated. Those experimental results provide boundary conditions for the discrete integration of Flamant＇s solutions, to inversely compute the separated components of the contact stresses.
基金support by the National Natural Sci-ence Foundation of China(Grant No.12274477)the De-partment of Science and Technology of Guangdong Provincein China(Grant No.2019QN01X061)。
文摘In moiré-patterned van der Waals structures of transition metal dichalcogenides,correlated insulators can form under integer and fractional fillings,whose transport properties are governed by various quasiparticle excitations including holons,doublons and interlayer exciton insulators.Here we theoretically investigate the nearest-neighbor inter-site hoppings of holons and interlayer exciton insulators.Our analysis indicates that these hopping strengths are significantly enhanced compared to that of a single carrier.The underlying mechanism can be attributed to the strong Coulomb interaction between carriers at different sites.For the interlayer exciton insulator consisting of a holon and a carrier in different layers,we have also obtained its effective Bohr radius and energy splitting between the ground and the first-excited states.
基金supported by Tencent’s Program of Aspiring Explorers in Sciencesupport by the National Natural Science Foundation of China (Grant No. 12274477)the Department of Science and Technology of Guangdong Province in China (Grant No. 2019QN01X061)。
文摘We theoretically investigated the chiral phonons of honeycomb-type bilayer Wigner crystals recently discovered in van der Waals structures of layered transition metal dichalcogenides. These chiral phonons can emerge under the inversion symmetry breaking introduced by an effective mass imbalance between the two layers or a moiré potential in one layer, as well as under the time-reversal symmetry breaking realized by applying a magnetic field. Considering the wide tunability of layered materials, the frequencies and chirality of phonons can both be tuned by varying the system parameters. These findings suggest that bilayer honeycomb-type Wigner crystals can serve as an exciting new platform for studying chiral phonons.
基金support by the National Natural Science Foundation of China(Grant No.12274477)the Department of Science and Technology of Guangdong Province of China(Grant No.2019QN01X061)。
文摘Using the Lindemann criterion,we analyzed the quantum and thermal melting of electronic/excitonic crystals recently discovered in two-dimensional(2D)semiconductor moirépatterns.We show that the finite 2D screening of the atomically thin material can suppress(enhance)the inter-site Coulomb(dipolar)interaction strength,thus inhibits(facilitates)the formation of the electronic(excitonic)crystal.Meanwhile,a strong enough moiréconfinement is found to be essential for realizing the crystal phase with a wavelength near 10 nm or shorter.From the calculated Lindemann ratio which quantifies the fluctuation of the site displacement,we estimate that the crystal will melt into a liquid above a critical temperature ranging from several tens Kelvin to above 100 K(depending on the system parameters).
文摘Moiré patterns on HOPG were studied with scanning tunneling microscopy （STM）. The results reveal that the observed Moiré patterns originate from the defects locating several layers below the surface, which presents the first experimental evidence supporting the prediction that in HOPG the nanoscale electronic waves can propagate through several layers without obvious decay.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 90406022 and 10674159）.
文摘We report on the formation of a graphene monolayer on a Ru（0001） surface by annealing the Ru（0001） crystal. The samples are characterized by scanning tunnelling microscopy （STM） and Auger electron spectroscopy （AES）. STM images show that the Moire pattern is caused by the graphene layer mismatched with the underlying Ru（0001） surface and has an N × N superlattice. It is further found that the graphene monolayer on a Ru（0001） surface is very stable at high temperatures. Our results provide a simple and convenient method to produce a graphene monolayer on the Ru（0001） surface, which is used as a template for fabricating functional nanostructures needed in future nano devices and catalysis.
基金This work was financially supported by the Key Technologies R&D Program of Guangdong Province, China (No. 2004B10301009).
文摘Sintered permanent magnetic strontium ferrites were studied using transmission electron microscopy to investigate the microstructure morphology and its correlation with the magnetic properties. The present study shows that the microstructure of sintered permanent magnetic strontium ferrites is an important parameter in determining their magnetic properties. The microstructure morphology in low-performance ferrite magnet is obviously different from high-performance one. The magnetic properties of sintered permanent strontium ferrite depend strongly on the orientation degree of strong magnetic crystals. The presence of ferric oxide phase in ferrite magnet can deteriorate the magnetic properties. Moreover, proper quantities of crystal defects are beneficial to high coercive force due to the fixing of magnetic domain.
基金National Natural Science Foundation of China(12074371)CAS Interdisciplinary Innovation Team,Strategic Priority Research Program of Chinese Academy of Sciences(XDB28000000)。
文摘Moirépatterns in physics are interference fringes produced when a periodic template is stacked on another similar one with different displacement and twist angles.The phonon in two-dimensional(2D)material affected by moirépatterns in the lattice shows various novel physical phenomena,such as frequency shift,different linewidth,and mediation to the superconductivity.This review gives a brief overview of phonons in 2D moirésuperlattice.First,we introduce the theory of the moiréphonon modes based on a continuum approach using the elastic theory and discuss the effect of the moirépattern on phonons in 2D materials such as graphene and MoS_(2).Then,we discuss the electron-phonon coupling(EPC)modulated by moirépatterns,which can be detected by the spectroscopy methods.Furthermore,the phonon-mediated unconventional superconductivity in 2D moirésuperlattice is introduced.The theory of phonon-mediated superconductivity in moirésuperlattice sets up a general framework,which promises to predict the response of superconductivity to various perturbations,such as disorder,magnetic field,and electric displacement field.
文摘This article considers collectively some of the most recent advances in the application of microscopicaland microanalytical techniques in materials science. including studies concerning rare metals. These comprise the highest resolution obtained with electron microscopy. observation of moire patterns in transmisionelectron microscopy (TEM), electro-dimpling before ion beam thinning as an effective step in the preparation of TEM samples, hydrogen problem in atom probe analysis, and a novel analysis technique-lasermicroprobe mass spectrometry (LAMMS).
文摘The distinct images of intragranular VC were observed on TEM in superalloy GH36 underwent normal heat treatment and prolonged aging.The size of VC particles were meas- ured by means of Moire pattern,and the misfit between VC and austenite was also calculated. The M23C6 enveloped in VC shell was also observed in the prolonged-aged specimens.The coherent relation between intragranular M_(23)C_6 twins and austenite as well as its coherent in- terface were also studied.
基金We acknowledge the financial support from the National Natural Science Foundation of China(No.51905306)the China Postdoctoral Science Fund(No.2018M642650)the Special Support for Post-doc Creative Funding of Shandong Province(No.201902005).We are also grateful for the funding support from the University of Manchester Donator Foundation and Swedish Research Council Formas(No.2019-01538).Dr.Chloe Holyord from National Graphene Institute,University of M anchester is gratefully acknowledged for the help with AFM m easurem ents.Dr.Linqing Zhang and Mr.Malachy Mcgowan are greatly acknowledged for the experimental support in the sample preparation.
文摘Moirépatterns from two-dimensional(2D)graphene heterostructures assembled via van der Waals interactions have sparked considerable interests in physics with the purpose to tailor the electronic properties of graphene.Here we report for the first time the observation of moire patterns arising from a bilayer graphone/graphene superlattice produced through direct single-sided hydrogenation of a bilayer graphene on substrate.Compared to pristine graphene,the bilayer superlattice exhibits a rippled surface and two types of moire patterns are observed:triangular and linear moire patterns with the periodicities of 11 nm and 8-9 nm,respectively.These moire patterns are revealed from atomic force microscopy and further confirmed by following fast Fourier transform(FFT)analysis.Density functional theory(DFT)calculations are also performed and the optimized lattice constants of bilayer superlattice heterostructure are in line with our experimental analysis.These findings show that well-defined triangular and linear periodic potentials can be introduced into the graphene system through the single-sided hydrogenation and also open a route towards the tailoring of electronic properties of graphene by various moirépotentials.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1405304)the National Natural Science Foundation of China(Grant No.12004118).
文摘Recently,the simulation of moiréphysics using cold atom platforms has gained significant attention.These platforms provide an opportunity to explore novel aspects of moiréphysics that go beyond the limits of traditional condensed matter systems.Building on recent experimental advancements in creating twisted bilayer spin-dependent optical lattices for pseudospin-1/2 Bose gases,we extend this concept to a trilayer optical lattice for spin-1 Bose gases.Unlike conventional moirépatterns,which are typically induced by interlayer tunneling or interspin coupling,the moirépattern in this trilayer system arises from inter-species atomic interactions.We investigate the ground state of Bose-Einstein condensates loaded in this spin-1 twisted optical lattice under both ferromagnetic and antiferromagnetic interactions.We find that the ground state forms a periodic pattern of distinct phases in the homogeneous case,including ferromagnetic,antiferromagnetic,polar,and broken axial symmetry phases.Additionally,by quenching the optical lattice potential strength,we examine the quench dynamics of the system above the ground state and observe the emergence of topological excitations such as vortex pairs.This study provides a pathway for exploring the rich physics of spin-1 twisted optical lattices and expands our understanding of moirésystems in synthetic quantum platforms.
基金the Ministry of Science and Technology of China(Nos.2019YFA0308600,2020YFA0309000,2016YFA0301003,and 2016YFA0300403)the National Natural Science Foundation of China(NSFC)(Nos.11521404,11634009,92065201,11874256,11874258,12074247,11790313,and 11861161003)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB28000000)the Science and Technology Commission of Shanghai Municipality(Nos.2019SHZDZX01,19JC1412701,and 20QA1405100)partial support.GYW is funded by China Postdoctoral Science Foundation(No.2021M693095)。
文摘Moire superlattice has recently been found in topological insulators,which can lead to periodic modulation on the electronic structure.In this work,we report the low-temperature scanning tunneling microscopy study of Sb_(2)Te_(3) films grown on graphitized 4H-SiC.We find that substrate temperature can strongly influence the rotation angles between Sb_(2)Te_(3) film and graphene substrate.Three kinds of moire patterns are observed at the first quintuple layer Sb_(2)Te_(3) film under different substrate temperatures.One shows complicated patterns with a rotation angle of nearly 0°relative to the substrate,another just exhibits simple 1 ×1 structure with a rotation angle of 30°.Other rotation angle like 8.2°is observed at higher substrate temperature as well,which is relatively rare.Comparison of the d//dV curves from Sb_(2)Te_(3) films with different moire patterns indicates that the superstructure can offer degrees of freedom in tailoring electronic structure.This work may stimulate the further study on the moire modulation to the electronic properties of topological insulators.
基金supported by the National Natural Science Foundation of China(No.52072308)the Open Project of Basic Research of Shandong Laboratory of Yantai Advanced Materials and Green Manufacturing(No.AMGM2022F02).
文摘Two-dimensional materials are excellent lubricants with inherent advantages.However,superlubricity has been reported for only a few of these materials.Unfortunately,other promising two-dimentional(2D)materials with different physical properties cannot be discovered or applied in production;thus,energy consumption can be greatly reduced.Here,we carry out high-throughput calculations for 1,4752D materials and screen for low-friction materials.To set a standard,we propose,for the first time,a geometry-independent lubricating figure of merit based on the conditions for stick-slip transition and our theory of Moiréfriction.For the efficient calculation of this figure of merit,an innovative approach was developed based on an improved registry index model.Through calculations,340 materials were found to have a figure of merit lower than 10−3.Eventually,a small set of 21 materials with a figure of merit lower than 10−4 were screened out.These materials can provide diverse choices for various applications.In addition,the efficient computational approach demonstrated in this work can be used to study other stacking-dependent properties.
基金the Key-Area Research and Development Program of Guangdong Province(2019B030330001)Research Grants Council of Hong Kong(17312916)Seed Funding for Strategic Interdisciplinary Research Scheme of HKU。
文摘Moiré interlayer exciton in transition metal dichalcogenide heterobilayer features a permanent electric dipole that enables the electrostatic control of its flow, and optical dipole that is spatially varying in the moiré landscape. We show the hybridization of moiré interlayer exciton with photons in a planar 2D cavity leads to two types of moiré polaritons that exhibit distinct forms of topological transport phenomena including the spin/valley Hall and polarization Hall effects, which feature remarkable electrical tunability through the control of exciton-cavity detuning by the interlayer bias.
基金Acknowledgements This work was financially supported by the National Natural Science Foundation of China （Grant Nos. 20973013, 51072004, 50821061, 20833001, 21073003, 20973006, and 50802003） and the Ministry of Science and Technology of China （Grant Nos. 2007CB936203, 2011CB921903, and 2009CB929403）. Ruiqi Zhao also thanks the Doctoral Foundation of Henan Polytechnic University （Grant No. B2009-90）.
文摘Microscopic features of graphene segregated on Ni films prior to chemical transfer--including atomic structures of monolayers and bilayers, Moire patterns due to non-AB stacking, as well as wrinkles and ripples caused by strain effects-have been characterized in detail by high-resolution scanning tunneling microscopy （STM）. We found that the stacking geometry of the bilayer graphene usually deviates from the traditional Bernal stacking （or so-called AB stacking）, resulting in the formation of a variety of Moir6 patterns. The relative rotations inside the bilayer were then qualitatively deduced from the relationship between Moir6 patterns and carbon lattices. Moreover, we found that typical defects such as wrinkles and ripples tend to evolve around multi-step boundaries of Ni, thus reflecting strong perturbations from substrate corrugations. These investigations of the morphology and the mechanism of formation of wrinkles and ripples are fundamental topics in graphene research. This work is expected to contribute to the exploration of electronic and transport properties of wrinkles and ripples.
