We theoretically investigate the quantum interference theory of magnetotransport of the three-component or spin-1 chiral fermions, which possess two linear Dirac bands and a flat band. For isotropic scalar impurities,...We theoretically investigate the quantum interference theory of magnetotransport of the three-component or spin-1 chiral fermions, which possess two linear Dirac bands and a flat band. For isotropic scalar impurities, the correction of conductivity from the coherent backscatter and non-coherent backscatter contributions cancel out in the intravalley scattering, leading to a weak localization correction to the Drude conductivity from the intervalley scattering. For the anisotropic impurities, the above cancelation is removed, we find the approximative quantum interference conductivity in the weak anisotropy case. The contributions from the chiral anomaly and classical Lorentz force are also discussed. Our work reveals some intriguing and detectable transport signatures of the novel spin-1 chiral fermions.展开更多
Electron-electron interactions(EEIs),quantum interference,and the effects of disorder on transport properties are essential topics in condensed matter physics.A series of our characterization work demonstrates that th...Electron-electron interactions(EEIs),quantum interference,and the effects of disorder on transport properties are essential topics in condensed matter physics.A series of our characterization work demonstrates that the morphology of Bi_(2)Te_(3)/MnTe bilayer film mainly depends on the magnetic substrate's growth mode and thickness.We propose that the temperature-dependent quantum interference of the electron wave function caused by disorder drives the transition from weak antilocalization(WAL) to weak localization(WL).Due to spin regulation,WL under low fields originates from the ferromagnetism in MnTe.The quantum interference effect(QIE) model analysis gives the degree of impurity scattering of the electron wave function.The electron wave is scattered by impurities,which causes the Berry phase to change from π to 0,producing a complete WL behavior.The stacked structure provides tunable degrees of freedom,allowing for independent optimization of topological properties and magnetic order through preferential growth orientation of topological insulator(TI) and magnetic layers,respectively.展开更多
Weak-localization （WL） measurements were performed in a Bi cluster-decorated graphene sheet. The charge concentration was kept constant, and the amplitude of the conductance correction was sup- pressed after the Bi-...Weak-localization （WL） measurements were performed in a Bi cluster-decorated graphene sheet. The charge concentration was kept constant, and the amplitude of the conductance correction was sup- pressed after the Bi-cluster deposition. Detailed WL data were obtained while the gate and temperature were changed. Using E. McCamfs ibrmula, the spin-relaxation time was extracted, which was found to increase with the elastic scattering time. This is attributed to the Elliott-Yafet spin relaxation and Kane-Mele type spin--orbit coupling （SOC）. The SOC strength was enhanced to 2.64 meV as a result of the first deposition. The coverage effect is discussed according to the measurement after tim second deposition.展开更多
We report the magnetotransport and thermal properties of RuAs_(2) single crystal.RuAs_(2) exhibits semiconductor behavior and localization effect.The crossover from normal state to diffusive transport in the weak loca...We report the magnetotransport and thermal properties of RuAs_(2) single crystal.RuAs_(2) exhibits semiconductor behavior and localization effect.The crossover from normal state to diffusive transport in the weak localization(WL)state and then to variable range hopping(VRH)transport in the strong localization state has been observed.The transitions can be reflected in the measurement of resistivity and Seebeck coefficient.Negative magnetoresistance(NMR)emerges with the appearance of localization effect and is gradually suppressed in high magnetic field.The temperature dependent phase coherence length extracted from the fittings of NMR also indicates the transition from WL to VRH.The measurement of Hall effect reveals an anomaly of temperature dependent carrier concentration caused by localization effect.Our findings show that RuAs_(2) is a suitable platform to study the localized state.展开更多
EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a t...EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a topological phase transition and a predicted quantum anomalous Hall effect(QAHE)approaching the two-dimensional(2D)limit.Yet,studies of the influence of the dimensionality approaching 2D on the electronic transport properties of EuB_(6) are still scarce.In this work,EuB_(6) thin sheets with thicknesses ranging from 35μm to 180μm were successfully fabricated through careful mechanical polishing of high-quality EuB_(6) single crystals.The reduced thickness,temperature and magnetic field have a strong influence on the electronic transport properties,including the CNMR and carrier concentration of EuB_(6) thin sheets.As the thickness of EuB_(6) thin sheets decreases from 180μm to 35μm,the magnetization transition temperature and the corresponding suppressing temperature of the Kondo effect decrease from 15.2 K to 10.9 K,while the CNMR ratio increases from-87.2%to-90.8%.Furthermore,the weak antilocalization effect transits to a weak localization effect and the carrier concentration increases by 9.4%at 30 K in a 35μm EuB_(6) thin sheet compared to the value reported for a 180μm thin sheet.Our findings demonstrate an obvious tunable effect of the reduced dimensionality on the transport properties of EuB_(6) along with the temperature and magnetic field,which could provide a route to exploring the QAHE near the 2D limit in EuB_(6) and other topological semimetals.展开更多
An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are relate...An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are related to the CoFeB thickness.When the film is thicker than 3 nm,the side jump mechanism dominates and the weak locaUzation to AHC vanishes.For very thin CoFeB films,both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect,and the weak localization correction to AHC is observed.展开更多
We investigate the local quantum uncertainty(LQU)in weak measurement.An expression of weak LQU is explicitly determined.Also,we consider some cases of three special X states,Werner state,circulant two-qubit states,and...We investigate the local quantum uncertainty(LQU)in weak measurement.An expression of weak LQU is explicitly determined.Also,we consider some cases of three special X states,Werner state,circulant two-qubit states,and Heisenberg model via LQU in normal and weak measurements.We find that the LQU in weak measurement is weaker than the case of strong measurement.展开更多
It is proved that the global existence for the nonhomogeneous quasilinear wave equation with a localized weakly nonlinear dissipation in exterior domains.
The problem of art forgery and infringement is becoming increasingly prominent,since diverse self-media contents with all kinds of art pieces are released on the Internet every day.For art paintings,object detection a...The problem of art forgery and infringement is becoming increasingly prominent,since diverse self-media contents with all kinds of art pieces are released on the Internet every day.For art paintings,object detection and localization provide an efficient and ef-fective means of art authentication and copyright protection.However,the acquisition of a precise detector requires large amounts of ex-pensive pixel-level annotations.To alleviate this,we propose a novel weakly supervised object localization(WSOL)with background su-perposition erasing(BSE),which recognizes objects with inexpensive image-level labels.First,integrated adversarial erasing(IAE)for vanilla convolutional neural network(CNN)dropouts the most discriminative region by leveraging high-level semantic information.Second,a background suppression module(BSM)limits the activation area of the IAE to the object region through a self-guidance mechanism.Finally,in the inference phase,we utilize the refined importance map(RIM)of middle features to obtain class-agnostic loc-alization results.Extensive experiments are conducted on paintings,CUB-200-2011 and ILSVRC to validate the effectiveness of our BSE.展开更多
Two kinds of spin-dependent scattering effects (magnetic-impurity and spin-orbit scatterings) are investigated theoretically in a quasi-two-dimensional (quasi-2D) disordered electron system. By making use of the diagr...Two kinds of spin-dependent scattering effects (magnetic-impurity and spin-orbit scatterings) are investigated theoretically in a quasi-two-dimensional (quasi-2D) disordered electron system. By making use of the diagrammatic techniques in perturbation theory, we have calculated the dc conductivity and magnetoresistance due to weak-localization effects, the analytical expressions of them are obtained as functions of the interlayer hopping energy and the characteristic times: elastic, inelastic, magnetic and spin-orbit scattering times. The relevant dimensional crossover behavior from 3D to 2D with decreasing the interlayer coupling is discussed, and the condition for the crossover is shown to be dependent on the aforementioned scattering times. At low temperature there exists a spin-dependent-scattering-induced dimensional crossover in this system.展开更多
By making use of the diagrammatic techniques in perturbation theory,we have investigated the Hall effect in a quasi-two-dimensional disordered electron system.In the weakly localized regime,the analytical expression f...By making use of the diagrammatic techniques in perturbation theory,we have investigated the Hall effect in a quasi-two-dimensional disordered electron system.In the weakly localized regime,the analytical expression for quantum correction to Hall conductivity has been obtained using the Kubo formalism and quasiclassical approximation.The relevant dimensional crossover behavior from three dimensions to two dimensions with decreasing the interlayer hopping energy is discussed.The quantum interference effect is shown to have a vanishing correction t,o the Hall coefficient.展开更多
A single ZnO nanowire with intrinsic oxygen vacancies is utilized to fabricate four-contact device with focus ion beam lithography technique. Cathodoluminescent spectra indicate strong near-UV and green emission at bo...A single ZnO nanowire with intrinsic oxygen vacancies is utilized to fabricate four-contact device with focus ion beam lithography technique. Cathodoluminescent spectra indicate strong near-UV and green emission at both room temperature and low temperatures. Experimental measurement shows the temperature-dependent conductivity of the ZnO nanowire at low temperatures （below 100 K）. The further theoretical analysis confirms that weak localization plays an important role in the electrical transport, which is attributed to the surface states induced by plenty of oxygen vacancies in ZnO nanowire.展开更多
Abstract Weak-localization effect in the presence of magnetic impurities is studied in disordered two-dimensional tight-binding square lattices around half filling. Both the magnetic and nonmagnetic impurities are ass...Abstract Weak-localization effect in the presence of magnetic impurities is studied in disordered two-dimensional tight-binding square lattices around half filling. Both the magnetic and nonmagnetic impurities are assumed to be randomly distributed on small fractions of the sites, while the nonmagnetic impurities have a strong potential yielding a unitary-limit scattering. We derive in details the expressions of diffusive π modes in the retarded-retarded （or advanced- advanced） channel, which result from the existence of particle-hole symmetry. The quantum interference correction to the density of states is calculated. While the magnetic-impurity scattering suppresses the quantum correction from π-mode cooperon, it does not affect the contribution of π-mode diffuson.展开更多
Three-dimensional topological insulators are a new class of quantum matter which has interesting connections to nearly all main branches of condensed matter physics. In this article, we briefly review the advances in ...Three-dimensional topological insulators are a new class of quantum matter which has interesting connections to nearly all main branches of condensed matter physics. In this article, we briefly review the advances in the field effect control of chemical potential in three-dimensional topological insulators. It is essential to the observation of many exotic quantum phenomena predicted to emerge from the topological insulators and their hybrid structures with other materials. We also describe various methods for probing the surface state transport. Some challenges in experimental study of electron transport in topological insulators will also be briefly discussed.展开更多
Interactions of magnetic elements with graphene may lead to various electronic states that have potential applications.We report an in-situ experiment in which the quantum transport properties of graphene are measured...Interactions of magnetic elements with graphene may lead to various electronic states that have potential applications.We report an in-situ experiment in which the quantum transport properties of graphene are measured with increasing cobalt coverage in continuous ultra-high vacuum environment.The results show that e-beam deposited cobalt forms clusters on the surface of graphene,even at low sample temperatures.Scattering of charge carriers by the absorbed cobalt clusters results in the disappearance of the Shubnikov–de Haas(Sd H)oscillations and the appearance of negative magnetoresistance(MR)which shows no sign of saturation up to an applied magnetic field of 9 T.We propose that these observations could originate from quantum interference driven by cobalt disorder and can be explained by the weak localization theory.展开更多
In this article, we prove the following results： （1） A Banach space X is weak midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively weakly compact k-Chebyshev set; （2） A ...In this article, we prove the following results： （1） A Banach space X is weak midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively weakly compact k-Chebyshev set; （2） A Banach space X is midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively compact k-Chebyshev set.展开更多
Let R be a commutative Noetherian ring and p be a prime ideal of R such that the ideal pRp is principal and ht(p)≠0. In this note, the anthors describe the explicit structure of the injective envelope of the R-module...Let R be a commutative Noetherian ring and p be a prime ideal of R such that the ideal pRp is principal and ht(p)≠0. In this note, the anthors describe the explicit structure of the injective envelope of the R-module R/p.展开更多
In this paper,we prove existence results of soutions for the nonlinear implicit complementarity problems NICP(T,S,K) where K is a closed weakly locally compact convex cone in a reflexive Banach space E,T is a nonlinea...In this paper,we prove existence results of soutions for the nonlinear implicit complementarity problems NICP(T,S,K) where K is a closed weakly locally compact convex cone in a reflexive Banach space E,T is a nonlinear operator from K into E* (i. e.,the dual space of E) and S is a nonlinear operator from K into E. Our results are the essential improvements and extension of the results obtained previously by several authors including Thera,Ding,and Zeng.展开更多
Weakly supervised object localization mines the pixel-level location information based on image-level annotations.The traditional weakly supervised object localization approaches exploit the last convolutional feature...Weakly supervised object localization mines the pixel-level location information based on image-level annotations.The traditional weakly supervised object localization approaches exploit the last convolutional feature map to locate the discriminative regions with abundant semantics.Although it shows the localization ability of classification network,the process lacks the use of shallow edge and texture features,which cannot meet the requirement of object integrity in the localization task.Thus,we propose a novel shallow feature-driven dual-edges localization(DEL)network,in which dual kinds of shallow edges are utilized to mine entire target object regions.Specifically,we design an edge feature mining(EFM)module to extract the shallow edge details through the similarity measurement between the original class activation map and shallow features.We exploit the EFM module to extract two kinds of edges,named the edge of the shallow feature map and the edge of shallow gradients,for enhancing the edge details of the target object in the last convolutional feature map.The total process is proposed during the inference stage,which does not bring extra training costs.Extensive experiments on both the ILSVRC and CUB-200-2011 datasets show that the DEL method obtains consistency and substantial performance improvements compared with the existing methods.展开更多
In this paper,the author proves that if the dual X^(*)of X is weakly locally uniformly convex and the convex function f is continuous on X,then there exist two sequences{f_(n)}_(n=1)^(∞)and{g_(n)}_(n=1)^(∞)of contin...In this paper,the author proves that if the dual X^(*)of X is weakly locally uniformly convex and the convex function f is continuous on X,then there exist two sequences{f_(n)}_(n=1)^(∞)and{g_(n)}_(n=1)^(∞)of continuous functions on X^(**)such that(1)f_(n)(x)≤f_(n+1)(x)≤f(x)≤g_(n+1)(x)≤g_(n)(x)whenever x∈X;(2)the two convex functions f_(n)and g_(n)are Gâteaux differentiable on X;(3)f_(n)→f and g_(n)→f uniformly on X.Moreover,if the function f is coercive on X,then(1)f_(n)and g_(n)are two w^(*)-lower semicontinuous convex functions on X^(**);(2)epif_(n)=epif_(n)∩(X×R)^(w)^(*)andg_(n)=epig_(n)∩(X×R)^(w)^(*).展开更多
基金partially supported by the High Magnetic Field Laboratory of Anhui Province,China。
文摘We theoretically investigate the quantum interference theory of magnetotransport of the three-component or spin-1 chiral fermions, which possess two linear Dirac bands and a flat band. For isotropic scalar impurities, the correction of conductivity from the coherent backscatter and non-coherent backscatter contributions cancel out in the intravalley scattering, leading to a weak localization correction to the Drude conductivity from the intervalley scattering. For the anisotropic impurities, the above cancelation is removed, we find the approximative quantum interference conductivity in the weak anisotropy case. The contributions from the chiral anomaly and classical Lorentz force are also discussed. Our work reveals some intriguing and detectable transport signatures of the novel spin-1 chiral fermions.
基金financially supported by the National Natural Science Foundation of China (Nos.52371204, 52201233,and 52031014)
文摘Electron-electron interactions(EEIs),quantum interference,and the effects of disorder on transport properties are essential topics in condensed matter physics.A series of our characterization work demonstrates that the morphology of Bi_(2)Te_(3)/MnTe bilayer film mainly depends on the magnetic substrate's growth mode and thickness.We propose that the temperature-dependent quantum interference of the electron wave function caused by disorder drives the transition from weak antilocalization(WAL) to weak localization(WL).Due to spin regulation,WL under low fields originates from the ferromagnetism in MnTe.The quantum interference effect(QIE) model analysis gives the degree of impurity scattering of the electron wave function.The electron wave is scattered by impurities,which causes the Berry phase to change from π to 0,producing a complete WL behavior.The stacked structure provides tunable degrees of freedom,allowing for independent optimization of topological properties and magnetic order through preferential growth orientation of topological insulator(TI) and magnetic layers,respectively.
文摘Weak-localization （WL） measurements were performed in a Bi cluster-decorated graphene sheet. The charge concentration was kept constant, and the amplitude of the conductance correction was sup- pressed after the Bi-cluster deposition. Detailed WL data were obtained while the gate and temperature were changed. Using E. McCamfs ibrmula, the spin-relaxation time was extracted, which was found to increase with the elastic scattering time. This is attributed to the Elliott-Yafet spin relaxation and Kane-Mele type spin--orbit coupling （SOC）. The SOC strength was enhanced to 2.64 meV as a result of the first deposition. The coverage effect is discussed according to the measurement after tim second deposition.
基金Project supported by the National Key Research and Development Program of China (Grant Nos.2023YFA1406500 and 2019YFA0308602)the National Natural Science Foundation of China (Grant Nos.12104011,12274388,12074425,52102333,12104010,12204004,and 11874422)the Natural Science Foundation of Anhui Province (Grant Nos.2108085QA22 and 2108085MA16)。
文摘We report the magnetotransport and thermal properties of RuAs_(2) single crystal.RuAs_(2) exhibits semiconductor behavior and localization effect.The crossover from normal state to diffusive transport in the weak localization(WL)state and then to variable range hopping(VRH)transport in the strong localization state has been observed.The transitions can be reflected in the measurement of resistivity and Seebeck coefficient.Negative magnetoresistance(NMR)emerges with the appearance of localization effect and is gradually suppressed in high magnetic field.The temperature dependent phase coherence length extracted from the fittings of NMR also indicates the transition from WL to VRH.The measurement of Hall effect reveals an anomaly of temperature dependent carrier concentration caused by localization effect.Our findings show that RuAs_(2) is a suitable platform to study the localized state.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1204100)the National Natural Science Foundation of China(Grant No.62488201)+1 种基金the Chinese Academy of Sciences(Grant Nos.XDB33030000 and YSBR-053)Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a topological phase transition and a predicted quantum anomalous Hall effect(QAHE)approaching the two-dimensional(2D)limit.Yet,studies of the influence of the dimensionality approaching 2D on the electronic transport properties of EuB_(6) are still scarce.In this work,EuB_(6) thin sheets with thicknesses ranging from 35μm to 180μm were successfully fabricated through careful mechanical polishing of high-quality EuB_(6) single crystals.The reduced thickness,temperature and magnetic field have a strong influence on the electronic transport properties,including the CNMR and carrier concentration of EuB_(6) thin sheets.As the thickness of EuB_(6) thin sheets decreases from 180μm to 35μm,the magnetization transition temperature and the corresponding suppressing temperature of the Kondo effect decrease from 15.2 K to 10.9 K,while the CNMR ratio increases from-87.2%to-90.8%.Furthermore,the weak antilocalization effect transits to a weak localization effect and the carrier concentration increases by 9.4%at 30 K in a 35μm EuB_(6) thin sheet compared to the value reported for a 180μm thin sheet.Our findings demonstrate an obvious tunable effect of the reduced dimensionality on the transport properties of EuB_(6) along with the temperature and magnetic field,which could provide a route to exploring the QAHE near the 2D limit in EuB_(6) and other topological semimetals.
基金supported by the National Basic Research Program of China(Grant No.2012CB933102)the National Natural Science Foundation of China(Grant Nos.11079052,11174354,and 51172080)
文摘An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are related to the CoFeB thickness.When the film is thicker than 3 nm,the side jump mechanism dominates and the weak locaUzation to AHC vanishes.For very thin CoFeB films,both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect,and the weak localization correction to AHC is observed.
文摘We investigate the local quantum uncertainty(LQU)in weak measurement.An expression of weak LQU is explicitly determined.Also,we consider some cases of three special X states,Werner state,circulant two-qubit states,and Heisenberg model via LQU in normal and weak measurements.We find that the LQU in weak measurement is weaker than the case of strong measurement.
文摘It is proved that the global existence for the nonhomogeneous quasilinear wave equation with a localized weakly nonlinear dissipation in exterior domains.
基金This work was supported in part by Guangdong Provincial Key Laboratory of Artificial Intelligence in Medical Image Analysis and Application,China(No.2022B1212010011).
文摘The problem of art forgery and infringement is becoming increasingly prominent,since diverse self-media contents with all kinds of art pieces are released on the Internet every day.For art paintings,object detection and localization provide an efficient and ef-fective means of art authentication and copyright protection.However,the acquisition of a precise detector requires large amounts of ex-pensive pixel-level annotations.To alleviate this,we propose a novel weakly supervised object localization(WSOL)with background su-perposition erasing(BSE),which recognizes objects with inexpensive image-level labels.First,integrated adversarial erasing(IAE)for vanilla convolutional neural network(CNN)dropouts the most discriminative region by leveraging high-level semantic information.Second,a background suppression module(BSM)limits the activation area of the IAE to the object region through a self-guidance mechanism.Finally,in the inference phase,we utilize the refined importance map(RIM)of middle features to obtain class-agnostic loc-alization results.Extensive experiments are conducted on paintings,CUB-200-2011 and ILSVRC to validate the effectiveness of our BSE.
基金Science Foundation of Southeast University of China，国家自然科学基金
文摘Two kinds of spin-dependent scattering effects (magnetic-impurity and spin-orbit scatterings) are investigated theoretically in a quasi-two-dimensional (quasi-2D) disordered electron system. By making use of the diagrammatic techniques in perturbation theory, we have calculated the dc conductivity and magnetoresistance due to weak-localization effects, the analytical expressions of them are obtained as functions of the interlayer hopping energy and the characteristic times: elastic, inelastic, magnetic and spin-orbit scattering times. The relevant dimensional crossover behavior from 3D to 2D with decreasing the interlayer coupling is discussed, and the condition for the crossover is shown to be dependent on the aforementioned scattering times. At low temperature there exists a spin-dependent-scattering-induced dimensional crossover in this system.
文摘By making use of the diagrammatic techniques in perturbation theory,we have investigated the Hall effect in a quasi-two-dimensional disordered electron system.In the weakly localized regime,the analytical expression for quantum correction to Hall conductivity has been obtained using the Kubo formalism and quasiclassical approximation.The relevant dimensional crossover behavior from three dimensions to two dimensions with decreasing the interlayer hopping energy is discussed.The quantum interference effect is shown to have a vanishing correction t,o the Hall coefficient.
基金supported by the National Natural Science Foundation of China (Grant Nos 60771037 and 90406022)the National High Technology Research and Development Program of China (Grant No 2008AA03Z309)the National Key Basic Research Program of China (Grant Nos 2007CB936802 and 2007CB935503)
文摘A single ZnO nanowire with intrinsic oxygen vacancies is utilized to fabricate four-contact device with focus ion beam lithography technique. Cathodoluminescent spectra indicate strong near-UV and green emission at both room temperature and low temperatures. Experimental measurement shows the temperature-dependent conductivity of the ZnO nanowire at low temperatures （below 100 K）. The further theoretical analysis confirms that weak localization plays an important role in the electrical transport, which is attributed to the surface states induced by plenty of oxygen vacancies in ZnO nanowire.
基金the Program for New Century Excellent Talents in Universities of China，中国科学院资助项目
文摘Abstract Weak-localization effect in the presence of magnetic impurities is studied in disordered two-dimensional tight-binding square lattices around half filling. Both the magnetic and nonmagnetic impurities are assumed to be randomly distributed on small fractions of the sites, while the nonmagnetic impurities have a strong potential yielding a unitary-limit scattering. We derive in details the expressions of diffusive π modes in the retarded-retarded （or advanced- advanced） channel, which result from the existence of particle-hole symmetry. The quantum interference correction to the density of states is calculated. While the magnetic-impurity scattering suppresses the quantum correction from π-mode cooperon, it does not affect the contribution of π-mode diffuson.
基金supported by the National Basic Research Program of China (Grant Nos. 2012CB921703 and 2009CB929101)the National Natural Science Foundation of China (Grant No. 91121003)the Chinese Academy of Sciences
文摘Three-dimensional topological insulators are a new class of quantum matter which has interesting connections to nearly all main branches of condensed matter physics. In this article, we briefly review the advances in the field effect control of chemical potential in three-dimensional topological insulators. It is essential to the observation of many exotic quantum phenomena predicted to emerge from the topological insulators and their hybrid structures with other materials. We also describe various methods for probing the surface state transport. Some challenges in experimental study of electron transport in topological insulators will also be briefly discussed.
基金the National Basic Research Program of China(Grant Nos.2013CB921900 and 2014CB920900)the National Natural Science Foundation of China(Grant No.11374021)the National Key Research and Development Program of China(Grant No.2018YFA0305604)
文摘Interactions of magnetic elements with graphene may lead to various electronic states that have potential applications.We report an in-situ experiment in which the quantum transport properties of graphene are measured with increasing cobalt coverage in continuous ultra-high vacuum environment.The results show that e-beam deposited cobalt forms clusters on the surface of graphene,even at low sample temperatures.Scattering of charge carriers by the absorbed cobalt clusters results in the disappearance of the Shubnikov–de Haas(Sd H)oscillations and the appearance of negative magnetoresistance(MR)which shows no sign of saturation up to an applied magnetic field of 9 T.We propose that these observations could originate from quantum interference driven by cobalt disorder and can be explained by the weak localization theory.
基金supported by the National Natural Science Foundation of China(11671252)supported by the National Natural Science Foundation of China(11771278)
文摘In this article, we prove the following results： （1） A Banach space X is weak midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively weakly compact k-Chebyshev set; （2） A Banach space X is midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively compact k-Chebyshev set.
基金This research is in part supported by a grant from IPM.
文摘Let R be a commutative Noetherian ring and p be a prime ideal of R such that the ideal pRp is principal and ht(p)≠0. In this note, the anthors describe the explicit structure of the injective envelope of the R-module R/p.
文摘In this paper,we prove existence results of soutions for the nonlinear implicit complementarity problems NICP(T,S,K) where K is a closed weakly locally compact convex cone in a reflexive Banach space E,T is a nonlinear operator from K into E* (i. e.,the dual space of E) and S is a nonlinear operator from K into E. Our results are the essential improvements and extension of the results obtained previously by several authors including Thera,Ding,and Zeng.
基金This work was partly supported by National Natural Science Foundation of China(No.62072394)Natural Science Foundation of Hebei Province,China(No.F2021203019)Hebei Key Laboratory Project,China(No.202250701010046).
文摘Weakly supervised object localization mines the pixel-level location information based on image-level annotations.The traditional weakly supervised object localization approaches exploit the last convolutional feature map to locate the discriminative regions with abundant semantics.Although it shows the localization ability of classification network,the process lacks the use of shallow edge and texture features,which cannot meet the requirement of object integrity in the localization task.Thus,we propose a novel shallow feature-driven dual-edges localization(DEL)network,in which dual kinds of shallow edges are utilized to mine entire target object regions.Specifically,we design an edge feature mining(EFM)module to extract the shallow edge details through the similarity measurement between the original class activation map and shallow features.We exploit the EFM module to extract two kinds of edges,named the edge of the shallow feature map and the edge of shallow gradients,for enhancing the edge details of the target object in the last convolutional feature map.The total process is proposed during the inference stage,which does not bring extra training costs.Extensive experiments on both the ILSVRC and CUB-200-2011 datasets show that the DEL method obtains consistency and substantial performance improvements compared with the existing methods.
基金supported by the National Natural Science Foundation of China(No.12271121).
文摘In this paper,the author proves that if the dual X^(*)of X is weakly locally uniformly convex and the convex function f is continuous on X,then there exist two sequences{f_(n)}_(n=1)^(∞)and{g_(n)}_(n=1)^(∞)of continuous functions on X^(**)such that(1)f_(n)(x)≤f_(n+1)(x)≤f(x)≤g_(n+1)(x)≤g_(n)(x)whenever x∈X;(2)the two convex functions f_(n)and g_(n)are Gâteaux differentiable on X;(3)f_(n)→f and g_(n)→f uniformly on X.Moreover,if the function f is coercive on X,then(1)f_(n)and g_(n)are two w^(*)-lower semicontinuous convex functions on X^(**);(2)epif_(n)=epif_(n)∩(X×R)^(w)^(*)andg_(n)=epig_(n)∩(X×R)^(w)^(*).
