A topological theory of liquid crystal films in the presence of defects is developed based on the Ф-mapping topological current theory. By generalizing the free-energy density in ＂one-constant＂ approximation, a cov...A topological theory of liquid crystal films in the presence of defects is developed based on the Ф-mapping topological current theory. By generalizing the free-energy density in ＂one-constant＂ approximation, a covariant free- energy density is obtained, from which the U（1） gauge field and the unified topological current for monopoles and strings in liquid crystals are derived. The inner topological structure of these topological defects is characterized by the winding numbers of Ф-mapping.展开更多
Based on Duan＇s topological current theory,we propose a novel approach to study the topological properties of topological defects in a two-dimensional complex vector order parameter system.This method shows explicitl...Based on Duan＇s topological current theory,we propose a novel approach to study the topological properties of topological defects in a two-dimensional complex vector order parameter system.This method shows explicitly the fine topological structure of defects.The branch processes of defects in the vector order parameter system have also been investigated with this method.展开更多
In this study, we focus into the non-relativistic wave equation described by the Schrodinger equation, specifically considering angular-dependent potentials within the context of a topological defect background genera...In this study, we focus into the non-relativistic wave equation described by the Schrodinger equation, specifically considering angular-dependent potentials within the context of a topological defect background generated by a cosmic string. Our primary goal is to explore quasi-exactly solvable problems by introducing an extended ring-shaped potential. We utilize the Bethe ansatz method to determine the angular solutions, while the radial solutions are obtained using special functions. Our findings demonstrate that the eigenvalue solutions of quantum particles are intricately influenced by the presence of the topological defect of the cosmic string,resulting in significant modifications compared to those in a flat space background. The existence of the topological defect induces alterations in the energy spectra, disrupting degeneracy.Afterwards, we extend our analysis to study the same problem in the presence of a ring-shaped potential against the background of another topological defect geometry known as a point-like global monopole. Following a similar procedure, we obtain the eigenvalue solutions and analyze the results. Remarkably, we observe that the presence of a global monopole leads to a decrease in the energy levels compared to the flat space results. In both cases, we conduct a thorough numerical analysis to validate our findings.展开更多
In this Letter,we explore the interplay between topological defects and resonant phenomena in photonic crystal slabs,focusing on quasi-flatband resonances and bound states in the continuum(BICs).We identify anisotropi...In this Letter,we explore the interplay between topological defects and resonant phenomena in photonic crystal slabs,focusing on quasi-flatband resonances and bound states in the continuum(BICs).We identify anisotropic quasi-flatband resonances and isotropic quasi-flatband symmetry-protected BICs that exist in coupled topological defects characterized by nontrivial 2D Zak phases,originating from monopole,dipole,and quadrupole corner modes within second-order topological insulator systems.These topological defect modes,whose band structures are described using a tight-binding model,exhibit distinctive radiative behavior due to their symmetry and multipolar characteristics.Through far-field excitation analysis,we demonstrate the robustness and accessibility of these modes in terms of angular and spectral stability.Furthermore,we investigate potential applications of the quasi-flatband resonances in light-matter interactions,including optical forces,second-harmonic generation,and strong coupling,which exhibit robust performance under varying illumination angles.These findings offer new opportunities for precise control over light-matter interactions.展开更多
It is most desirable to realize efficient photocatalytic hydrogen peroxide production through rational molecular design.Here we show a novel approach through the rational control of topological defects in the covalent...It is most desirable to realize efficient photocatalytic hydrogen peroxide production through rational molecular design.Here we show a novel approach through the rational control of topological defects in the covalent organic framework(COF)to significantly boost photocatalytic H_(2)O_(2)production.Using the same organic building blocks,we can build both the defective COF and nondefective COF through control of the reaction conditions.The as-synthesized defective COF enables a H_(2)O_(2)production rate as high as 5347μmol g^(−1)h^(−1)in the absence of any sacrificial agent,exceeding most reported materials for such use,while the nondefective counterpart affords a lower H_(2)O_(2)production rate of 1975μmol g^(−1)h^(−1).This means that the control of the topological defect in COF can endow a 2.7-fold enhancement in the H_(2)O_(2)production.Mechanism research reveals the oxygen reduction reaction route for H_(2)O_(2)production from O_(2)coupling with the water oxidation reaction(WOR)to generate O_(2)from water,where the defect site plays a vital role in the WOR.Furthermore,we develop an innovative mineralization strategy for selective extraction of uranium,in light of the excellent H_(2)O_(2)production performance in the defective COF,which can enhance the efficiency of uranium extraction by 4.9-fold and selectivity for uranium over other metal ions by three orders of magnitude relative to the common one-step photocatalysis.展开更多
Nonradical oxidation based on peroxydisulfate(PDS)activation has attracted increasing attention for selective degradation of organic pollutants.Herein,topological defects were introduced into biochar(BC)via removing N...Nonradical oxidation based on peroxydisulfate(PDS)activation has attracted increasing attention for selective degradation of organic pollutants.Herein,topological defects were introduced into biochar(BC)via removing N atoms in N-doped BC(NBC)in an attempt to improve the nonradical catalytic performance.Compared to the pristine BC and NBC,the introduction of topological defects could achieve up to 36.6-and 8.7-times catalytic activity enhancement,respectively.More importantly,it was found that the catalytic activity was dominated by topological defects,which was verified by the significant positive correlation between the pseudo-first-order rate constants and the content of topological defects.Theoretical calculations suggested that topological defects enhanced the electrondonating ability of BC by reducing the energy gap,which made the electrons transfer to PDS molecules more easily.As a result,holes were generated after the carbon defects lost electrons,and induced a nonradical oxidation process.Benefiting from the merits of nonradical oxidation,the developed BC/PDS system showed superior performance in removing electron-rich contaminants in the presence of inorganic anions and in the actual environments.This study not only provides a potential avenue for designing efficient biochar-based catalysts,but also advances the mechanism understanding of nonradical oxidation process induced by carbon defects.展开更多
Owing to the complexity of electron transfer pathways,the sluggish oxygen evolution reaction process is defined as the bottleneck for the practical application of Zn-air batteries.In this effort,metal nanoparticles(Co...Owing to the complexity of electron transfer pathways,the sluggish oxygen evolution reaction process is defined as the bottleneck for the practical application of Zn-air batteries.In this effort,metal nanoparticles(Co,Ni,Fe,etc.)encapsulated within nitrogen-doped carbon materials with abundant edge sites were synthesized by one-step pyrolysis treatment using cigarette butts as raw materials,which can drastically accelerate the overall rate of oxygen evolution reaction by facilitating the adsorption of oxygenated intermediates by the edge-induced topological defects.The prepared catalyst of nitrogen-doped carbon porous nanosheets loaded with Co nanoparticles(Co@NC-500)exhibits enhanced catalytic activity toward oxygen evolution reaction,with a low overpotential of 350 mV at the current density of 10 mA·cm^(-2).Furthermore,the Zn-air battery assembled with Co@NC-500 catalyst demonstrates a desirable performance affording an open-circuit potential of 1.336 V and power density of 33.6 mW·cm^(-2),indicating considerable practical application potential.展开更多
Electronic charge order is a symmetry breaking state in high-Tc cuprate superconductors. In scanning tunneling microscopy, the detected charge-order-induced modulation is an electronic response of the charge order. Fo...Electronic charge order is a symmetry breaking state in high-Tc cuprate superconductors. In scanning tunneling microscopy, the detected charge-order-induced modulation is an electronic response of the charge order. For an overdoped(Bi,Pb)2Sr2CuO6+x sample, we apply scanning tunneling microscopy to explore local properties of the charge order. The ordering wavevector is nondispersive with energy, which can be confirmed and determined. By extracting its order-parameter field, we identify dislocations in the stripe structure of the electronic modulation, which correspond to topological defects with an integer winding number of ±1. Through differential conductance maps over a series of reduced energies, the development of different response of the charge order is observed and a spatial evolution of topological defects is detected. The intensity of charge-order-induced modulation increases with energy and reaches its maximum when approaching the pseudogap energy. In this evolution, the topological defects decrease in density and migrate in space. Furthermore, we observe appearance and disappearance of closely spaced pairs of defects as energy changes. Our experimental results could inspire further studies of the charge order in both high-Tccuprate superconductors and other charge density wave materials.展开更多
Topological insulators/superconductors are new states of quantum matter with metallic edge/surface states.In this paper,we review the defects effect in these topological states and study new types of topological matte...Topological insulators/superconductors are new states of quantum matter with metallic edge/surface states.In this paper,we review the defects effect in these topological states and study new types of topological matters — topological hierarchy matters.We find that both topological defects（quantized vortices） and non topological defects（vacancies） can induce topological mid-gap states in the topological hierarchy matters after considering the superlattice of defects.These topological mid-gap states have nontrivial topological properties,including the nonzero Chern number and the gapless edge states.Effective tight-binding models are obtained to describe the topological mid-gap states in the topological hierarchy matters.展开更多
Based on the complex three-component order parameter model of a spin-triplet superconductor, by using the C-mapping theory, we derive a new equation describing the distribution of the magnetic field for vortices, whic...Based on the complex three-component order parameter model of a spin-triplet superconductor, by using the C-mapping theory, we derive a new equation describing the distribution of the magnetic field for vortices, which can be reduced to the modified London equation in the case of ｜ψ^2｜^2 ^- ｜ψ^3｜^2 = 0 and Wl^1= 1. A magnetic flux quantization condition for vortices in a spin-triplet superconductor is also derived, which is topological-invariant. Fhrthermore, the branch processes during the evolution of the vortices in a spin-triplet superconductor are discussed. We also point out that the sum of the magnetic flux quantization that those vortices carried is 2nФo （Фo is the unit magnetic flux）, that is to say, the sum of winding number is even, which needs to be proved by experiment.展开更多
By making use of Duan-Ge＇s decomposition theory of gauge potential and the topological current theory proposed by Prof. Duan Yi-Shi, we study a two-component superfluid Bose condensed system, which is supposed to be ...By making use of Duan-Ge＇s decomposition theory of gauge potential and the topological current theory proposed by Prof. Duan Yi-Shi, we study a two-component superfluid Bose condensed system, which is supposed to be realized in the interior of neutron stars in the form of the coexistence of a neutron superfluid and a protonic superconductor. We propose that this system possesses vortex lines. The topological charges of the vortex lines are characterized by the Hopf indices and the Brower degrees of C-mapping.展开更多
In this paper, using the Φ-mapping theory, it is shown that two kinds of topological defects, i.e., the vortex lines and the monopoles exist in the helical configuration of magnetic field in triplet superconductors. ...In this paper, using the Φ-mapping theory, it is shown that two kinds of topological defects, i.e., the vortex lines and the monopoles exist in the helical configuration of magnetic field in triplet superconductors. And the inner topological structure of these defects is studied. Because the knot solitons in the triplet superconductors are characterized by the Hopf invariant, we also establish a relationship between the Hopf invariant and the linking number of knots family, and reveal the inner topological structure of the Hopf invariant.展开更多
In this paper,we investigate the quantum dynamics of a non-relativistic particle confined by the Aharonov-Bohm quantum flux field with pseudoharmonic-type potential in the background of topological defect produced by ...In this paper,we investigate the quantum dynamics of a non-relativistic particle confined by the Aharonov-Bohm quantum flux field with pseudoharmonic-type potential in the background of topological defect produced by a point-like global monopole.We solve the radial Schrödinger equation analytically and determine the exact eigenvalue solution of the quantum system.Afterwards,we consider a Mie-type potential in the quantum system and solve the radial equation analytically and obtain the eigenvalue solution.We analyze the effects of the topological defect and the quantum flux with these potentials on the energy eigenvalue and wave function of the nonrelativistic particles.In fact,it is shown that the energy levels and wave functions are influenced by the topological defect shifted the result compared to the flat space results.In addition,the quantum flux field also shifted the eigenvalue solutions and an analogue of the Aharonov-Bohm effect for bound-states is observed.Finally,we utilize these eigenvalue solutions to some known diatomic molecular potential models and presented the energy eigenvalue and wave function.展开更多
Zigzag graphene nanoribbon （ZGNR） is a promising candidate for next-generation spintronic devices. Development of the field requires potential systems with variable and adjustable electromagnetic properties. Here we...Zigzag graphene nanoribbon （ZGNR） is a promising candidate for next-generation spintronic devices. Development of the field requires potential systems with variable and adjustable electromagnetic properties. Here we show a detailed investigation of ZGNR decorated with edge topological defects （ED-ZGNR） synthesized in laboratory by Ruffieux in 2015 [Pascal Ruffieux, Shiyong Wang, Bo Yang, et al. 2015 Nature 531 489]. The pristine ED-ZGNR in the ground state is an antiferromagnetic semiconductor, and the acquired band structure is significantly changed compared with that of perfect ZGNR. After doping heteroatoms on the edge, the breaking of degeneration of band structure makes the doped ribbon a half-semi-metal, and nonzero magnetic moments are induced. Our results indicate the tunable electronic and magnetic properties of ZGNR by deriving unique edge state from topological defect, which opens a new route to practical nano devices based on ZGNR.展开更多
We investigate the ground-state phases and spin textures of spin-orbit-coupled dipolar pseudo-spin-1/2 Bose-Einstein condensates in a rotating two-dimensional toroidal potential.The combined effects of dipole-dipole i...We investigate the ground-state phases and spin textures of spin-orbit-coupled dipolar pseudo-spin-1/2 Bose-Einstein condensates in a rotating two-dimensional toroidal potential.The combined effects of dipole-dipole interaction(DDI),spin-orbit coupling(SOC),rotation,and interatomic interactions on the ground-state structures and topological defects of the system are analyzed systematically.For fixed SOC strength and rotation frequency,we provide a set of phase diagrams as a function of the DDI strength and the ratio between inter-and intra-species interactions.The system can show rich quantum phases including a half-quantum vortex,symmetrical(asymmetrical)phase with quantum droplets(QDs),asymmetrical segregated phase with hidden vortices(ASH phase),annular condensates with giant vortices,triangular(square)vortex lattice with QDs,and criss-cross vortex string lattice,depending on the competition between DDI and contact interaction.For given DDI strength and rotation frequency,the increase of the SOC strength leads to a structural phase transition from an ASH phase to a tetragonal vortex lattice then to a pentagonal vortex lattice and finally to a vortex necklace,which is also demonstrated by the momentum distributions.Without rotation,the interplay of DDI and SOC may result in the formation of a unique trumpet-shaped Bloch domain wall.In addition,the rotation effect is discussed.Furthermore,the system supports exotic topological excitations,such as a half-skyrmion(meron)string,triangular skyrmion lattice,skyrmion-halfskyrmion lattice,skyrmion-meron cluster,skyrmion-meron layered necklace,skyrmion-giant-skyrmion necklace lattice,and half-skyrmion-half-antiskyrmion necklace.展开更多
The dilemmas posed by dark matter and dark energy have been with us for decades without a satisfactory resolution. We propose that both DM and DE can be explained by the existence of long-lived topological gravitation...The dilemmas posed by dark matter and dark energy have been with us for decades without a satisfactory resolution. We propose that both DM and DE can be explained by the existence of long-lived topological gravitational vortices that were produced in the quark-gluon epoch of cosmic inflation due to the misalignment of the gravitational and strong forces. This is analogous to the misalignment mechanism proposed for the production of axions in the early universe. The masses of these topological vortices are expected to be on the order of the nucleon mass. Possible means for their detection are discussed.展开更多
The formation and evolution of cosmic string wakes in the framework of a <i>f</i>(<i>R</i>) theory of gravity are investigated in this work. We consider a simple model in which baryonic matter ...The formation and evolution of cosmic string wakes in the framework of a <i>f</i>(<i>R</i>) theory of gravity are investigated in this work. We consider a simple model in which baryonic matter flows past a cosmic string. We treat this problem in the Zel’dovich approximation. We compare our results with previous results obtained in the context of General Relativity and Scalar-Theories of Gravity.展开更多
In the light of C-mapping method and topological current theory, the stability of disclinations around a spherical particle in nematic liquid crystals is studied. We consider two different defect structures around a s...In the light of C-mapping method and topological current theory, the stability of disclinations around a spherical particle in nematic liquid crystals is studied. We consider two different defect structures around a spherical particle： disclination ring and point defect at the north or south pole of the particle. We calculate the free energy of these different defects in the elastic theory. It is pointed out that the total Frank free energy density can be divided into two parts. One is the distorted energy density of director field around the disclinations. The other is the free energy density of disclinations themselves, which is shown to be concentrated at the defect and to be topologically quantized in the unit of （k - k24）π/2. It is shown that in the presence of saddle-splay elasticity a dipole （radial and hyperbolic hedgehog） configuration that accompanies a particle with strong homeotropic anchoring takes the structure of a small disclination ring, not a point defect.展开更多
The non-equilibrium dynamics of a one-dimensional(1 D)topological system with 3 rd-nearest-neighbor hopping has been investigated by analytical and numerical methods.An analytical form of topological defect density un...The non-equilibrium dynamics of a one-dimensional(1 D)topological system with 3 rd-nearest-neighbor hopping has been investigated by analytical and numerical methods.An analytical form of topological defect density under the periodic boundary conditions(PBC)is obtained by using the Landau-Zener formula(LZF),which is consistent with the scaling of defect production provided by the Kibble-Zurek mechanism(KZM).Under the open boundary conditions(OBC),quench dynamics becomes more complicated due to edge states.The behaviors of the system quenching across different phases show that defect production no longer satisfies the KZM paradigm since complicated couplings exist under OBC.Some new dynamical features are revealed.展开更多
The switching characteristics of ferroelectrics and multiferroics are influenced by the interaction of topological defects with domain walls.We report on the pinning of polarization due to antiphase boundaries in thin...The switching characteristics of ferroelectrics and multiferroics are influenced by the interaction of topological defects with domain walls.We report on the pinning of polarization due to antiphase boundaries in thin films of the multiferroic hexagonal YbFeO_(3).We have directly resolved the atomic structure of a sharp antiphase boundary(APB)in YbFeO_(3) thin films using a combination of aberration-corrected scanning transmission electron microscopy(STEM)and total energy calculations based on density-functional theory(DFT).We find the presence of a layer of FeO_(6) octahedra at the APB that bridges the adjacent domains.STEM imaging shows a reversal in the direction of polarization on moving across the APB,which DFT calculations confirm is structural in nature as the polarization reversal reduces the distortion of the FeO_(6) octahedral layer at the APB.Such APBs in hexagonal perovskites are expected to serve as domain-wall pinning sites and hinder ferroelectric switching of the domains.展开更多
文摘A topological theory of liquid crystal films in the presence of defects is developed based on the Ф-mapping topological current theory. By generalizing the free-energy density in ＂one-constant＂ approximation, a covariant free- energy density is obtained, from which the U（1） gauge field and the unified topological current for monopoles and strings in liquid crystals are derived. The inner topological structure of these topological defects is characterized by the winding numbers of Ф-mapping.
基金Project supported by the National Natural Science Foundation of China (Grant No 10275030)Cuiying Project of Lanzhou University of China (Grant No 225000-582404)
文摘Based on Duan＇s topological current theory,we propose a novel approach to study the topological properties of topological defects in a two-dimensional complex vector order parameter system.This method shows explicitly the fine topological structure of defects.The branch processes of defects in the vector order parameter system have also been investigated with this method.
文摘In this study, we focus into the non-relativistic wave equation described by the Schrodinger equation, specifically considering angular-dependent potentials within the context of a topological defect background generated by a cosmic string. Our primary goal is to explore quasi-exactly solvable problems by introducing an extended ring-shaped potential. We utilize the Bethe ansatz method to determine the angular solutions, while the radial solutions are obtained using special functions. Our findings demonstrate that the eigenvalue solutions of quantum particles are intricately influenced by the presence of the topological defect of the cosmic string,resulting in significant modifications compared to those in a flat space background. The existence of the topological defect induces alterations in the energy spectra, disrupting degeneracy.Afterwards, we extend our analysis to study the same problem in the presence of a ring-shaped potential against the background of another topological defect geometry known as a point-like global monopole. Following a similar procedure, we obtain the eigenvalue solutions and analyze the results. Remarkably, we observe that the presence of a global monopole leads to a decrease in the energy levels compared to the flat space results. In both cases, we conduct a thorough numerical analysis to validate our findings.
基金supported by the National Key Research and Development Program of China(No.2022YFF0706005)the National Natural Science Foundation of China(Nos.62305387,12272407,62275269,and 62275271)+1 种基金the Natural Science Foundation of Hunan Province(No.2023JJ40683)the National University of Defense Technology(No.ZK23-03)。
文摘In this Letter,we explore the interplay between topological defects and resonant phenomena in photonic crystal slabs,focusing on quasi-flatband resonances and bound states in the continuum(BICs).We identify anisotropic quasi-flatband resonances and isotropic quasi-flatband symmetry-protected BICs that exist in coupled topological defects characterized by nontrivial 2D Zak phases,originating from monopole,dipole,and quadrupole corner modes within second-order topological insulator systems.These topological defect modes,whose band structures are described using a tight-binding model,exhibit distinctive radiative behavior due to their symmetry and multipolar characteristics.Through far-field excitation analysis,we demonstrate the robustness and accessibility of these modes in terms of angular and spectral stability.Furthermore,we investigate potential applications of the quasi-flatband resonances in light-matter interactions,including optical forces,second-harmonic generation,and strong coupling,which exhibit robust performance under varying illumination angles.These findings offer new opportunities for precise control over light-matter interactions.
基金supported financially by the Open Project Program of National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing(grant no.2024QZ-TD-18)the National Natural Science Foundations of China(grant no.22376024)the Jiangxi project(grant no.DHSQT22021007).The authors would also like to thank Wenqian Liu from Shiyanjia Lab(www.Shiyanjia.com)for the X-ray diffraction analysis.
文摘It is most desirable to realize efficient photocatalytic hydrogen peroxide production through rational molecular design.Here we show a novel approach through the rational control of topological defects in the covalent organic framework(COF)to significantly boost photocatalytic H_(2)O_(2)production.Using the same organic building blocks,we can build both the defective COF and nondefective COF through control of the reaction conditions.The as-synthesized defective COF enables a H_(2)O_(2)production rate as high as 5347μmol g^(−1)h^(−1)in the absence of any sacrificial agent,exceeding most reported materials for such use,while the nondefective counterpart affords a lower H_(2)O_(2)production rate of 1975μmol g^(−1)h^(−1).This means that the control of the topological defect in COF can endow a 2.7-fold enhancement in the H_(2)O_(2)production.Mechanism research reveals the oxygen reduction reaction route for H_(2)O_(2)production from O_(2)coupling with the water oxidation reaction(WOR)to generate O_(2)from water,where the defect site plays a vital role in the WOR.Furthermore,we develop an innovative mineralization strategy for selective extraction of uranium,in light of the excellent H_(2)O_(2)production performance in the defective COF,which can enhance the efficiency of uranium extraction by 4.9-fold and selectivity for uranium over other metal ions by three orders of magnitude relative to the common one-step photocatalysis.
基金National Key Research and Development Program of China(2021YFC1809204)National Natural Science Foundation of China(42192573,21621005,and U21A20163)+1 种基金Research and Development Program of Zhejiang Province,China(2021C0167)Fundamental Research Funds for the Central Universities(226-2022-00212).
文摘Nonradical oxidation based on peroxydisulfate(PDS)activation has attracted increasing attention for selective degradation of organic pollutants.Herein,topological defects were introduced into biochar(BC)via removing N atoms in N-doped BC(NBC)in an attempt to improve the nonradical catalytic performance.Compared to the pristine BC and NBC,the introduction of topological defects could achieve up to 36.6-and 8.7-times catalytic activity enhancement,respectively.More importantly,it was found that the catalytic activity was dominated by topological defects,which was verified by the significant positive correlation between the pseudo-first-order rate constants and the content of topological defects.Theoretical calculations suggested that topological defects enhanced the electrondonating ability of BC by reducing the energy gap,which made the electrons transfer to PDS molecules more easily.As a result,holes were generated after the carbon defects lost electrons,and induced a nonradical oxidation process.Benefiting from the merits of nonradical oxidation,the developed BC/PDS system showed superior performance in removing electron-rich contaminants in the presence of inorganic anions and in the actual environments.This study not only provides a potential avenue for designing efficient biochar-based catalysts,but also advances the mechanism understanding of nonradical oxidation process induced by carbon defects.
基金the National Natural Science Foundation of China(Grant Nos.22179065,22111530112)the S&T project from Shanghai Tobacco Group Co.Ltd.
文摘Owing to the complexity of electron transfer pathways,the sluggish oxygen evolution reaction process is defined as the bottleneck for the practical application of Zn-air batteries.In this effort,metal nanoparticles(Co,Ni,Fe,etc.)encapsulated within nitrogen-doped carbon materials with abundant edge sites were synthesized by one-step pyrolysis treatment using cigarette butts as raw materials,which can drastically accelerate the overall rate of oxygen evolution reaction by facilitating the adsorption of oxygenated intermediates by the edge-induced topological defects.The prepared catalyst of nitrogen-doped carbon porous nanosheets loaded with Co nanoparticles(Co@NC-500)exhibits enhanced catalytic activity toward oxygen evolution reaction,with a low overpotential of 350 mV at the current density of 10 mA·cm^(-2).Furthermore,the Zn-air battery assembled with Co@NC-500 catalyst demonstrates a desirable performance affording an open-circuit potential of 1.336 V and power density of 33.6 mW·cm^(-2),indicating considerable practical application potential.
基金supported by the National Basic Research Program of China(Grant No.2015CB921004)the National Natural Science Foundation of China(Grant No.11374260)+3 种基金financial support from the National Natural Science Foundation of China(Grant No.11334010)the Fundamental Research Funds for the Central Universities in Chinathe National Key Research and Development Program of China(Grant No.2016YFA0300300)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB07020300)
文摘Electronic charge order is a symmetry breaking state in high-Tc cuprate superconductors. In scanning tunneling microscopy, the detected charge-order-induced modulation is an electronic response of the charge order. For an overdoped(Bi,Pb)2Sr2CuO6+x sample, we apply scanning tunneling microscopy to explore local properties of the charge order. The ordering wavevector is nondispersive with energy, which can be confirmed and determined. By extracting its order-parameter field, we identify dislocations in the stripe structure of the electronic modulation, which correspond to topological defects with an integer winding number of ±1. Through differential conductance maps over a series of reduced energies, the development of different response of the charge order is observed and a spatial evolution of topological defects is detected. The intensity of charge-order-induced modulation increases with energy and reaches its maximum when approaching the pseudogap energy. In this evolution, the topological defects decrease in density and migrate in space. Furthermore, we observe appearance and disappearance of closely spaced pairs of defects as energy changes. Our experimental results could inspire further studies of the charge order in both high-Tccuprate superconductors and other charge density wave materials.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CB921803 and 2012CB921704)the National Natural Science Foundation of China(Grant Nos.11174035,11474025,11404090,and 11674026)+2 种基金the Natural Science Foundation of Hebei Province,China(Grant No.A2015205189)the Hebei Education Department Natural Science Foundation,China(Grant No.QN2014022)the Specialized Research Fund for the Doctoral Program of Higher Education,China
文摘Topological insulators/superconductors are new states of quantum matter with metallic edge/surface states.In this paper,we review the defects effect in these topological states and study new types of topological matters — topological hierarchy matters.We find that both topological defects（quantized vortices） and non topological defects（vacancies） can induce topological mid-gap states in the topological hierarchy matters after considering the superlattice of defects.These topological mid-gap states have nontrivial topological properties,including the nonzero Chern number and the gapless edge states.Effective tight-binding models are obtained to describe the topological mid-gap states in the topological hierarchy matters.
基金supported by National Natural Science Foundation of China and Cuiying Programme of Lanzhou University
文摘Based on the complex three-component order parameter model of a spin-triplet superconductor, by using the C-mapping theory, we derive a new equation describing the distribution of the magnetic field for vortices, which can be reduced to the modified London equation in the case of ｜ψ^2｜^2 ^- ｜ψ^3｜^2 = 0 and Wl^1= 1. A magnetic flux quantization condition for vortices in a spin-triplet superconductor is also derived, which is topological-invariant. Fhrthermore, the branch processes during the evolution of the vortices in a spin-triplet superconductor are discussed. We also point out that the sum of the magnetic flux quantization that those vortices carried is 2nФo （Фo is the unit magnetic flux）, that is to say, the sum of winding number is even, which needs to be proved by experiment.
基金supported by the National Natural Science Foundation of China (Grant No 10275030)Cuiying Project of Lanzhou University (Grant No 225000-582404)
文摘By making use of Duan-Ge＇s decomposition theory of gauge potential and the topological current theory proposed by Prof. Duan Yi-Shi, we study a two-component superfluid Bose condensed system, which is supposed to be realized in the interior of neutron stars in the form of the coexistence of a neutron superfluid and a protonic superconductor. We propose that this system possesses vortex lines. The topological charges of the vortex lines are characterized by the Hopf indices and the Brower degrees of C-mapping.
基金The project supported by National Natural Science Foundation of China under Grant No. 10275030 Acknowledgments 0ne of the authors, XU Dong-Hui, is indebted to Dr. LIU Yu-Xiao for useful discussions and help.
文摘In this paper, using the Φ-mapping theory, it is shown that two kinds of topological defects, i.e., the vortex lines and the monopoles exist in the helical configuration of magnetic field in triplet superconductors. And the inner topological structure of these defects is studied. Because the knot solitons in the triplet superconductors are characterized by the Hopf invariant, we also establish a relationship between the Hopf invariant and the linking number of knots family, and reveal the inner topological structure of the Hopf invariant.
文摘In this paper,we investigate the quantum dynamics of a non-relativistic particle confined by the Aharonov-Bohm quantum flux field with pseudoharmonic-type potential in the background of topological defect produced by a point-like global monopole.We solve the radial Schrödinger equation analytically and determine the exact eigenvalue solution of the quantum system.Afterwards,we consider a Mie-type potential in the quantum system and solve the radial equation analytically and obtain the eigenvalue solution.We analyze the effects of the topological defect and the quantum flux with these potentials on the energy eigenvalue and wave function of the nonrelativistic particles.In fact,it is shown that the energy levels and wave functions are influenced by the topological defect shifted the result compared to the flat space results.In addition,the quantum flux field also shifted the eigenvalue solutions and an analogue of the Aharonov-Bohm effect for bound-states is observed.Finally,we utilize these eigenvalue solutions to some known diatomic molecular potential models and presented the energy eigenvalue and wave function.
基金supported by the National Natural Science Foundation of China(Grant Nos.51474176,51674205,51575452,and 51475378)
文摘Zigzag graphene nanoribbon （ZGNR） is a promising candidate for next-generation spintronic devices. Development of the field requires potential systems with variable and adjustable electromagnetic properties. Here we show a detailed investigation of ZGNR decorated with edge topological defects （ED-ZGNR） synthesized in laboratory by Ruffieux in 2015 [Pascal Ruffieux, Shiyong Wang, Bo Yang, et al. 2015 Nature 531 489]. The pristine ED-ZGNR in the ground state is an antiferromagnetic semiconductor, and the acquired band structure is significantly changed compared with that of perfect ZGNR. After doping heteroatoms on the edge, the breaking of degeneration of band structure makes the doped ribbon a half-semi-metal, and nonzero magnetic moments are induced. Our results indicate the tunable electronic and magnetic properties of ZGNR by deriving unique edge state from topological defect, which opens a new route to practical nano devices based on ZGNR.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11475144 and 11047033)the Natural Science Foundation of Hebei Province,China(Grant Nos.A2019203049 and A2015203037)+2 种基金the University Science and Technology Foundation of Hebei Provincial Department of Education,China(Grant No.Z2017056)Science and Technology Plan Projects of Tangshan City,China(Grant No.19130220g)Research Foundation of Yanshan University,China(Grant No.B846).
文摘We investigate the ground-state phases and spin textures of spin-orbit-coupled dipolar pseudo-spin-1/2 Bose-Einstein condensates in a rotating two-dimensional toroidal potential.The combined effects of dipole-dipole interaction(DDI),spin-orbit coupling(SOC),rotation,and interatomic interactions on the ground-state structures and topological defects of the system are analyzed systematically.For fixed SOC strength and rotation frequency,we provide a set of phase diagrams as a function of the DDI strength and the ratio between inter-and intra-species interactions.The system can show rich quantum phases including a half-quantum vortex,symmetrical(asymmetrical)phase with quantum droplets(QDs),asymmetrical segregated phase with hidden vortices(ASH phase),annular condensates with giant vortices,triangular(square)vortex lattice with QDs,and criss-cross vortex string lattice,depending on the competition between DDI and contact interaction.For given DDI strength and rotation frequency,the increase of the SOC strength leads to a structural phase transition from an ASH phase to a tetragonal vortex lattice then to a pentagonal vortex lattice and finally to a vortex necklace,which is also demonstrated by the momentum distributions.Without rotation,the interplay of DDI and SOC may result in the formation of a unique trumpet-shaped Bloch domain wall.In addition,the rotation effect is discussed.Furthermore,the system supports exotic topological excitations,such as a half-skyrmion(meron)string,triangular skyrmion lattice,skyrmion-halfskyrmion lattice,skyrmion-meron cluster,skyrmion-meron layered necklace,skyrmion-giant-skyrmion necklace lattice,and half-skyrmion-half-antiskyrmion necklace.
文摘The dilemmas posed by dark matter and dark energy have been with us for decades without a satisfactory resolution. We propose that both DM and DE can be explained by the existence of long-lived topological gravitational vortices that were produced in the quark-gluon epoch of cosmic inflation due to the misalignment of the gravitational and strong forces. This is analogous to the misalignment mechanism proposed for the production of axions in the early universe. The masses of these topological vortices are expected to be on the order of the nucleon mass. Possible means for their detection are discussed.
文摘The formation and evolution of cosmic string wakes in the framework of a <i>f</i>(<i>R</i>) theory of gravity are investigated in this work. We consider a simple model in which baryonic matter flows past a cosmic string. We treat this problem in the Zel’dovich approximation. We compare our results with previous results obtained in the context of General Relativity and Scalar-Theories of Gravity.
基金The project supported by the Natural Science Foundation of Shanghai Municipal Commission of Science and Technology under Grant No. 04ZR14059, National Natural Science Foundation of China under Grant No. 10447125, and the Shanghai Municipal Science and Technology Commission under Grant No. 04dz05905
文摘In the light of C-mapping method and topological current theory, the stability of disclinations around a spherical particle in nematic liquid crystals is studied. We consider two different defect structures around a spherical particle： disclination ring and point defect at the north or south pole of the particle. We calculate the free energy of these different defects in the elastic theory. It is pointed out that the total Frank free energy density can be divided into two parts. One is the distorted energy density of director field around the disclinations. The other is the free energy density of disclinations themselves, which is shown to be concentrated at the defect and to be topologically quantized in the unit of （k - k24）π/2. It is shown that in the presence of saddle-splay elasticity a dipole （radial and hyperbolic hedgehog） configuration that accompanies a particle with strong homeotropic anchoring takes the structure of a small disclination ring, not a point defect.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974334,11574294,and 11774332)。
文摘The non-equilibrium dynamics of a one-dimensional(1 D)topological system with 3 rd-nearest-neighbor hopping has been investigated by analytical and numerical methods.An analytical form of topological defect density under the periodic boundary conditions(PBC)is obtained by using the Landau-Zener formula(LZF),which is consistent with the scaling of defect production provided by the Kibble-Zurek mechanism(KZM).Under the open boundary conditions(OBC),quench dynamics becomes more complicated due to edge states.The behaviors of the system quenching across different phases show that defect production no longer satisfies the KZM paradigm since complicated couplings exist under OBC.Some new dynamical features are revealed.
基金supported by the National Science Foundation(NSF)(Grant Nos.DMR-2122070,2145797,and 1454618)by the Nebraska Center for Energy Sciences Research(NCESR)supported by NSF grants#2138259,#2138286,#2138307,#2137603,and#2138296。
文摘The switching characteristics of ferroelectrics and multiferroics are influenced by the interaction of topological defects with domain walls.We report on the pinning of polarization due to antiphase boundaries in thin films of the multiferroic hexagonal YbFeO_(3).We have directly resolved the atomic structure of a sharp antiphase boundary(APB)in YbFeO_(3) thin films using a combination of aberration-corrected scanning transmission electron microscopy(STEM)and total energy calculations based on density-functional theory(DFT).We find the presence of a layer of FeO_(6) octahedra at the APB that bridges the adjacent domains.STEM imaging shows a reversal in the direction of polarization on moving across the APB,which DFT calculations confirm is structural in nature as the polarization reversal reduces the distortion of the FeO_(6) octahedral layer at the APB.Such APBs in hexagonal perovskites are expected to serve as domain-wall pinning sites and hinder ferroelectric switching of the domains.
