Recently,charged solitons have been found in a two-dimensional CoCl_(2)/HOPG system,whose microscopic nature remains to be elusive.In this work,we investigate the charged solitons in monolayer CoCl_(2) using scanning ...Recently,charged solitons have been found in a two-dimensional CoCl_(2)/HOPG system,whose microscopic nature remains to be elusive.In this work,we investigate the charged solitons in monolayer CoCl_(2) using scanning tunneling microscopy(STM)and atomic force microscopy(AFM).Moreover,we study the electrical properties of the charged solitons at zero electric field by measuring local contact potential difference(LCPD)via Kelvin probe force microscopy(KPFM)using the Δf(V)method.The compensation voltage corresponding to the vertex of the parabola is obtained by fitting the quadratic relationship between Δf and sample bias.The results show that,without an external electric field,the solitons behave as negatively charged entities.Meanwhile,the LCPD mapping characterizes the spatial distribution of the potential at the charged solitons,which agrees well with those obtained from STM band bending measurements.展开更多
With the rapid development of artificial intelligence technology,deep learning,as one of its core technologies,occupies an important position in the cultivation of applied talents.Based on the concept of integration o...With the rapid development of artificial intelligence technology,deep learning,as one of its core technologies,occupies an important position in the cultivation of applied talents.Based on the concept of integration of industry and education,this paper proposes a systematic teaching reform plan to address the issues of disconnection between theory and practice,single teaching methods,and insufficient practical resources in the deep learning courses for professional master’s students at our university.Through deep cooperation with Huawei Cloud Technologies Co.,Ltd.,we introduce cutting-edge theoretical content(such as GoogleNet,ResNet,Transformer,BERT,etc.),update practical cases(covering computer vision,natural language processing,and smart manufacturing),and adopt a case-led comprehensive teaching method combined with the online and offline hybrid practical platform ModelArts to promote the close integration of theory and practice.Simultaneously,a diversified evaluation system with practice as the core is constructed to comprehensively assess students’practical abilities and project execution levels.The research in this paper provides a valuable reference for the innovation of teaching modes and the cultivation of practical abilities in deep learning courses in higher education institutions.展开更多
With the development of artificial intelligence and deep learning,the attention mechanism has become a key technology for enhancing the performance of complex tasks.This paper reviews the evolution of attention mechan...With the development of artificial intelligence and deep learning,the attention mechanism has become a key technology for enhancing the performance of complex tasks.This paper reviews the evolution of attention mechanisms,including soft attention,hard attention,and recent innovations such as multi-head latent attention and cross-attention.It focuses on the latest research outcomes,such as lightning attention,the PADRe polynomial attention replacement algorithm,the context anchor attention module,and improvements in attention mechanisms for large models.These advancements improve the efficiency and accuracy of models,expanding the application potential of attention mechanisms in fields such as computer vision,natural language processing,and remote sensing object detection,aiming to provide readers with a comprehensive understanding and stimulate innovative thinking.展开更多
Epitaxial strain is an effective way to control thermoelectricity of a thin film system.In this work,we investigate strain-dependent thermoelectricity of[(SrTiO_(3))_(3)/(SrTi_(0.8)Nb_(0.2)O_(3))_(3)]_(10)superlattice...Epitaxial strain is an effective way to control thermoelectricity of a thin film system.In this work,we investigate strain-dependent thermoelectricity of[(SrTiO_(3))_(3)/(SrTi_(0.8)Nb_(0.2)O_(3))_(3)]_(10)superlattices grown on different substrates,including-0.96%on(LaAlO_(3))_(0.3)(SrAl_(0.5)Ta_(0.5)O_(3))_(0.7)(001)(LSAT),0%on SrTiO_(3)(001)(STO),+0.99%on DyScO_(3)(110)(DSO)and+1.64%on GdScO_(3)(110)(GSO),respectively.Our results show that the highest room-temperature thermoelectricity is achieved when the STO-based superlattice is grown on the DSO substrate with+0.99%tensile strain.This is attributed to the high permittivity and low dielectric loss arising from the ferroelectric domain and electron-phonon coupling,which boost the power factor(PF)to 10.5 mW·m^(-1)·K^(-2)at 300 K.展开更多
The increasing occurrence of pesticide micropollutants highlights the need for innovative water treatment technologies,particularly for small-community and household applications.Electro-oxidation is being widely stud...The increasing occurrence of pesticide micropollutants highlights the need for innovative water treatment technologies,particularly for small-community and household applications.Electro-oxidation is being widely studied in this area,unfortunately,safe,stable and efficient electrocatalytic anodes without released heavy metal ions are still highly required.In this study,we fabricated a Pt/Ti anode by high energy pulse magnetron sputtering(HiPIMS-PtTi)which was used to decompose dichlorvos(DDVP)and azoxystrobin(AZX)in water.The results show that the reaction rate constant(kENR)on HIPIMS was 35.7 min-1(DDVP)and 41.3 min-1(AZX),respectively,superior to electroplating Pt/Ti anode(EP-PtTi).The identification of radicals(^(·)OH,^(1)O_(2),^(·)O_(2)-)and micro-area analyses evidenced that Pt atoms were embedded into the TiO_(2) lattice on the surface of Ti plate by high-energy ions,which resulted in more adsorbed hydroxyls,and higher production of·OH under polarization conditions.Besides,the electro-oxidation intermediates of DDVP and AZX were identified and the degradation pathways were speculated:(1)indirect oxidation dominated by·OH attack,and(2)direct electron transfer reaction of pesticides on the anode surface.The cooperated reactions achieve the complete degradation and highly efficient mineralization of DDVP and AZX.展开更多
In two-dimensional(2D)materials,due to weak interlayer van der Waals(vdW)interaction,the crystal structure can be tuned through the control of interlayer stacking with a rather low increase in energy.Whereas most prev...In two-dimensional(2D)materials,due to weak interlayer van der Waals(vdW)interaction,the crystal structure can be tuned through the control of interlayer stacking with a rather low increase in energy.Whereas most previous work has focused on the electronic and optical properties associated with the vdW stacking,the recent discovery of magnetism in 2D materials extends this research area to magnetic properties.CrI3 and CrBr3 are two isostructural ferromagnetic 2D materials,which maintain out-of-plane ferromagnetism down to the monolayer limit.However,as confirmed through recent experiments based on mechanically exfoliated samples,CrI3 bilayers exhibit interlayer antiferromagnetism,while CrBr3 bilayers exhibit interlayer ferromagnetism.Such a striking difference in the magnetic properties between bilayers of CrI3 and CrBr3 prompts a thorough investigation of the mechanisms governing the interlayer magnetic coupling.展开更多
We report a significantly enhanced anomalous Hall effect(AHE)of Pt on antiferromagnetic insulator thin film(3-unit-cell La_(0.7)Sr_(0.3)MnO_(3),abbreviated as LSMO),which is one order of magnitude larger than that of ...We report a significantly enhanced anomalous Hall effect(AHE)of Pt on antiferromagnetic insulator thin film(3-unit-cell La_(0.7)Sr_(0.3)MnO_(3),abbreviated as LSMO),which is one order of magnitude larger than that of Pt on other ferromagnetic(e.g.Y_(3)Fe_(5)O_(12))and antiferromagnetic(e.g.Cr_(2)O_(3))insulator thin films.Our experiments demonstrate that the antiferromagnetic La_(0.7)Sr_(0.3)MnO_(3)with fully compensated surface suppresses the positive anomalous Hall resistivity induced by the magnetic proximity effect and facilitates the negative anomalous Hall resistivity induced by the spin Hall effect.By changing the substrate’s temperature during Pt deposition,we observed that the diffusion of Mn atoms into Pt layer can further enhance the AHE.The anomalous Hall resistivity increases with increasing temperature and persists even well above the Neel temperature(T_(N))of LSMO.The Monte Carlo simulations manifest that the unusual rise of anomalous Hall resistivity above T_(N)originates from the thermal induced magnetization in the antiferromagnetic insulator.展开更多
We reported a study of tunnel magnetoresistance(TMR)effect in single manganite nanowire via the combination of magnetotransport and magnetic force microscopy imaging.TMR value up to 290%has been observed in single(La1...We reported a study of tunnel magnetoresistance(TMR)effect in single manganite nanowire via the combination of magnetotransport and magnetic force microscopy imaging.TMR value up to 290%has been observed in single(La1-yPry)1-x CaxMnO3 nanowires with varying width.We find that the TMR effect can be explained in the scenario of opening and blockade of conducting channels from inherent magnetic domain evolutions.Our findings provide a new route to fabricate TMR junctions and point towards future improvements in complex oxide-based TMR spintronics.展开更多
A number of recent studies have demonstrated that electrochemical technologies, including electroreduction （ER）, electrocoagulation （EC）, and electrodialysis （ED）, are effbctive in nitrate elimination in wastewa...A number of recent studies have demonstrated that electrochemical technologies, including electroreduction （ER）, electrocoagulation （EC）, and electrodialysis （ED）, are effbctive in nitrate elimination in wastewater due to their high reactivity. To obtain the maximal elimination efficiency and current efficiency, many researchers have conducted experiments to investigate the optimal conditions （i.e., potential, cun＇ent density, pH value, plate distance, initial nitrate concentration, electrolyte, and other factors） tbr nitrate elimination. The mechanism of ER, EC and ED for nitrate removal has been fully elucidated. The ER mechanism of nitrate undergoes electron transfer and hydrogenation reduction. The EC pathways of nitrate removal include reduction, coagulation and flotation. The ED pathways of nitrate include redox reaction and dialysis. Although the electrochemical technology can remove nitrate from wastewater efficiently, many problems （such as relatively low selectivity toward nitrogen, sludge production and brine generation） still hinder electrochemical treatment implementa- tion. This paper critically presents an overview of the current state-of-the-art of electrochemical denitrification to enhance the removal efficiency and overcome the shortages, and will significantly improve the understanding of the detailed processes and mechanisms of nitrate removal by electrochemical treatment and provide useful information to scientific research and actual practice.展开更多
Numerous exotic properties have been discovered in Dirac Semimetals(DSMs) and Weyl Semimetals(WSMs). In a given DSM/WSM, the Dirac/Weyl nodes usually coexist with other bulk states, making their respective contributio...Numerous exotic properties have been discovered in Dirac Semimetals(DSMs) and Weyl Semimetals(WSMs). In a given DSM/WSM, the Dirac/Weyl nodes usually coexist with other bulk states, making their respective contribution elusive. In this work, we distinguish the role of bulk states from the tilted Dirac nodes on the transport properties in DSMs. Specifically, we applied pressure to a type-II DSM material, PtTe2, and studied its pressure modified electronic and lattice structure systematically by using in situ transport measurements and X-ray diffraction(XRD). A pressure-induced transition at about 20 GPa is revealed in the transport properties, while the layered lattice structure is robust against pressure as illustrated in XRD measurement results.Density functional theory(DFT) calculations suggest that this is originated from the Lifshitz transition in the bulk states. Our findings provide evidence to identify the bulk states' influence on transport from the topologically-protected DSM states in the DSM material.展开更多
Photocatalytic hydrogen production synergized with the oxidation of pollutants is an environmentally friendly and economical approach to generate clean energy and remove the pollution from environment.In this study,ph...Photocatalytic hydrogen production synergized with the oxidation of pollutants is an environmentally friendly and economical approach to generate clean energy and remove the pollution from environment.In this study,photocatalytic hydrogen production cooperating with 2,4,6-trichlorophenol(2,4,6-TCP)degradation have been reinforced by introducing an ultrasonic atomization.The degradation of 2,4,6-TCP in a mist of three photocatalysts(g-C3N4,TiO2,and Bi2O3)generated by ultrasonic atomization was performed under 254 nm ultraviolet(UV254)light irradiation.The results showed that,under UV254 irradiation,three different photocatalysts(g-C3N4,TiO2,and Bi2O3)all accelerated both hydrogen production and 2,4,6-TCP degradation.Additionally,2,4,6-TCP degradation and photocatalytic hydrogen production exhibited an obvious synergistic effect,since 2,4,6-TCP has a strong tendency to react with photo-generated holes and their second radicals so as to inhibit the recombination of carriers,and thus improved the efficiency of hydrogen production simultaneously.Moreover,by introducing ultrasonic atomization,the atomized droplets acted as micro-photocatalytic units to replace the macrophotocatalytic reaction reactor.Therefore,the mass transfer distance for free radicals was restricted and the utilization of light energy by photocatalysts was increased.Further,the reaction efficiency was improved.The results reveal environmentally friendly and economical potential of hydrogen production by photocatalytic degradation of 2,4,6-TCP in atomized droplets.展开更多
Complex oxides have rich functionalities and advantages for future technologies.In many systems,quenched disorder often holds the key to determine their physical properties,and these properties can be further tuned by...Complex oxides have rich functionalities and advantages for future technologies.In many systems,quenched disorder often holds the key to determine their physical properties,and these properties can be further tuned by chemical doping.However,understanding the role of quenched disorder is complicated because chemical doping simultaneously alters other physical variables such as local lattice distortions and electronic and magnetic environments.Here,we show that spatial confinement is an effective approach to tuning the level of quenched disorder in a complex-oxide system while leaving other physical variables largely undisturbed.Through the confinement of a manganite system down to quasi-one-dimensional nanowires,we observed that the nature of its metal-insulator phase transition exhibits a crossover from a discontinuous to a continuous characteristic,in close accordance with quenched disorder theories.We argue that the quenched disorder,finite size,and surface effects all contribute to our experimental observations.Noticeably,with reduced nanowire width,the magnetoresistance shows substantial enhancement at low temperatures.Our findings offer new insight into experimentally tuning the quenched disorder effect to achieve novel functionalities at reduced dimensions.展开更多
Light,acting as an external stimulus to induce various intriguing phenomena ranging from photovoltaics to photoinduced catalysis,exerts prominent effects in strongly correlated systems.It would be of particular intere...Light,acting as an external stimulus to induce various intriguing phenomena ranging from photovoltaics to photoinduced catalysis,exerts prominent effects in strongly correlated systems.It would be of particular interest to investigate photon-induced emerging phenomena in spatially confined strongly correlated systems,which are important for applications of these materials in future electronic devices.Colossal magnetoresistive manganites materials offer an ideal platform for such study due to their sensitivity to photo-excitation.Here,we fabricated 900 nm wide La_(0.325)Pr_(0.3)Ca_(0.375)Mn O_3strips,whose width is comparable to the size of the electronic phase separation(EPS)domains in this system.We observed the photoinduced critical fluctuations in the strips,where abrupt resistivity jumps occurred upon photoinduced phase transition depending sensitively on the light intensity.Based on the microscopic views of the EPS domains under photoexcitation,we conclude that such photo-induced resistivity fluctuations originate from the photoinduced phase fluctuations of individual EPS domains when their size becomes comparable to the strip width.展开更多
Manganese selenide （MnSe） possesses unique magnetic properties as an important magnetic semiconductor, but the synthesis and properties of MnSe nanocrystals are less developed compared to other semiconductor nanocry...Manganese selenide （MnSe） possesses unique magnetic properties as an important magnetic semiconductor, but the synthesis and properties of MnSe nanocrystals are less developed compared to other semiconductor nanocrystals because of the inability to obtain high-quality MnSe, especially in the metastable wurtzite structure. Here, we have successfully fabricated wurtzite MnSe nanocrystals via a colloidal approach which affords uniform crystal sizes and tailored shapes. The selective binding strength of the amine surfactant is the determining factor in shape-control and shape-evolution. Bullet-shapes could be transformed into shuttle-shapes if part of the oleylamine in the reaction solution was replaced by trioctylamine, and tetrapod-shaped nanocrystals could be formed in trioctylamine systems. The three-dimensional （3D） structure of the bullet-shaped nanorods has been demonstrated by the advanced transmission electron microscope （TEM） 3D-tomography technology. High-resolution TEM （HRTEM） and electron energy-loss spectroscopy （EELS） show that planar-defect structures such as stacking faults and twinning along the [001] direction arise during the growth of bullet-shapes. On the basis of careful HRTEM observations, we propose a ＂quadra-twin core＂ growth mechanism for the formation of wurtzite MnSe nanotetrapods. Furthermore, the wurtzite MnSe nanocrystals show low- temperature surface spin-glass behavior due to their noncompensated surface spins and the blocking temperatures increase from 8.4 K to 18.5 K with increasing surface area/volume ratio of the nanocrystals. Our results provide a systematic study of wurtzite MnSe nanocrystals.展开更多
In correlated oxides,collaborative manipulation on light intensity,wavelength,pulse duration and polarization has yielded many exotic discoveries,such as phase transitions and novel quantum states.In view of potential...In correlated oxides,collaborative manipulation on light intensity,wavelength,pulse duration and polarization has yielded many exotic discoveries,such as phase transitions and novel quantum states.In view of potential optoelectronic applications,tailoring long-lived static properties by light-induced effects is highly desirable.So far,the polarization state of light has rarely been reported as a control parameter for this purpose.Here,we report polarization-dependent metal-to-insulator transition(MIT)in phaseseparated manganite thin films,introducing a new degree of freedom to control static MIT.Specifically,we observed giant photoinduced resistance jumps with striking features:(1)a single resistance jump occurs upon a linearly polarized light incident with a chosen polarization angle,and a second resistance jump occurs when the polarization angle changes;(2)the amplitude of the second resistance jump depends sensitively on the actual change of the polarization angles.Linear transmittance measurements reveal that the origin of the above phenomena is closely related to the coexistence of anisotropic micro-domains.Our results represent a first step to utilize light polarization as an active knob to manipulate static phase transitions,pointing towards new pathways for nonvolatile optoelectronic devices and sensors.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403300 and 2019YFA0308404)the National Natural Science Foundation of China(Grant Nos.11427902,11991060,12074075,12474165,12274084,and 12241402)+5 种基金Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Shanghai Municipal Natural Science Foundation(Grant No.22ZR1407400)Innovation Program for Quantum Science and Technology(Grant No.2024ZD0300104)Innovation Program of Shanghai Municipal Education Commission(Grant No.2023ZKZD03)Science and Technology Commission of Shanghai Municipality(Grant No.20JC1415900)China Postdoctoral Science Foundation(Grant No.KLH1512149).
文摘Recently,charged solitons have been found in a two-dimensional CoCl_(2)/HOPG system,whose microscopic nature remains to be elusive.In this work,we investigate the charged solitons in monolayer CoCl_(2) using scanning tunneling microscopy(STM)and atomic force microscopy(AFM).Moreover,we study the electrical properties of the charged solitons at zero electric field by measuring local contact potential difference(LCPD)via Kelvin probe force microscopy(KPFM)using the Δf(V)method.The compensation voltage corresponding to the vertex of the parabola is obtained by fitting the quadratic relationship between Δf and sample bias.The results show that,without an external electric field,the solitons behave as negatively charged entities.Meanwhile,the LCPD mapping characterizes the spatial distribution of the potential at the charged solitons,which agrees well with those obtained from STM band bending measurements.
基金Ministry of Education Industry-Education Cooperation and Collaborative Education Project“Tool Abnormality Detection in the Field of Smart Manufacturing Based on Ascend AI Cloud Services”(241100007143750)Dalian Jiaotong University Undergraduate Teaching Quality and Education Teaching Reform Research Project“Research on the Reform of the Curriculum System of Software Engineering Integrating Artificial Intelligence Under the Background of New Engineering”(010702)。
文摘With the rapid development of artificial intelligence technology,deep learning,as one of its core technologies,occupies an important position in the cultivation of applied talents.Based on the concept of integration of industry and education,this paper proposes a systematic teaching reform plan to address the issues of disconnection between theory and practice,single teaching methods,and insufficient practical resources in the deep learning courses for professional master’s students at our university.Through deep cooperation with Huawei Cloud Technologies Co.,Ltd.,we introduce cutting-edge theoretical content(such as GoogleNet,ResNet,Transformer,BERT,etc.),update practical cases(covering computer vision,natural language processing,and smart manufacturing),and adopt a case-led comprehensive teaching method combined with the online and offline hybrid practical platform ModelArts to promote the close integration of theory and practice.Simultaneously,a diversified evaluation system with practice as the core is constructed to comprehensively assess students’practical abilities and project execution levels.The research in this paper provides a valuable reference for the innovation of teaching modes and the cultivation of practical abilities in deep learning courses in higher education institutions.
文摘With the development of artificial intelligence and deep learning,the attention mechanism has become a key technology for enhancing the performance of complex tasks.This paper reviews the evolution of attention mechanisms,including soft attention,hard attention,and recent innovations such as multi-head latent attention and cross-attention.It focuses on the latest research outcomes,such as lightning attention,the PADRe polynomial attention replacement algorithm,the context anchor attention module,and improvements in attention mechanisms for large models.These advancements improve the efficiency and accuracy of models,expanding the application potential of attention mechanisms in fields such as computer vision,natural language processing,and remote sensing object detection,aiming to provide readers with a comprehensive understanding and stimulate innovative thinking.
基金supported by the National Key Research&Development Program of China(Grant No.2022YFA1403300)the Innovation Program for Quantum Science and Technology(Grant No.2024ZD0300103)+2 种基金the National Natural Science Foundation of China(Grant Nos.11991060,11427902,12074075,62171136,and 12474165)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the Shanghai Municipal Natural Science Foundation(Grant Nos.22ZR1407400,22ZR1408100,and 23ZR1407200)。
文摘Epitaxial strain is an effective way to control thermoelectricity of a thin film system.In this work,we investigate strain-dependent thermoelectricity of[(SrTiO_(3))_(3)/(SrTi_(0.8)Nb_(0.2)O_(3))_(3)]_(10)superlattices grown on different substrates,including-0.96%on(LaAlO_(3))_(0.3)(SrAl_(0.5)Ta_(0.5)O_(3))_(0.7)(001)(LSAT),0%on SrTiO_(3)(001)(STO),+0.99%on DyScO_(3)(110)(DSO)and+1.64%on GdScO_(3)(110)(GSO),respectively.Our results show that the highest room-temperature thermoelectricity is achieved when the STO-based superlattice is grown on the DSO substrate with+0.99%tensile strain.This is attributed to the high permittivity and low dielectric loss arising from the ferroelectric domain and electron-phonon coupling,which boost the power factor(PF)to 10.5 mW·m^(-1)·K^(-2)at 300 K.
基金supported by National Natural Science Foundation of China(No.21777009)Beijing Natural Science Foundation(No.8182031).
文摘The increasing occurrence of pesticide micropollutants highlights the need for innovative water treatment technologies,particularly for small-community and household applications.Electro-oxidation is being widely studied in this area,unfortunately,safe,stable and efficient electrocatalytic anodes without released heavy metal ions are still highly required.In this study,we fabricated a Pt/Ti anode by high energy pulse magnetron sputtering(HiPIMS-PtTi)which was used to decompose dichlorvos(DDVP)and azoxystrobin(AZX)in water.The results show that the reaction rate constant(kENR)on HIPIMS was 35.7 min-1(DDVP)and 41.3 min-1(AZX),respectively,superior to electroplating Pt/Ti anode(EP-PtTi).The identification of radicals(^(·)OH,^(1)O_(2),^(·)O_(2)-)and micro-area analyses evidenced that Pt atoms were embedded into the TiO_(2) lattice on the surface of Ti plate by high-energy ions,which resulted in more adsorbed hydroxyls,and higher production of·OH under polarization conditions.Besides,the electro-oxidation intermediates of DDVP and AZX were identified and the degradation pathways were speculated:(1)indirect oxidation dominated by·OH attack,and(2)direct electron transfer reaction of pesticides on the anode surface.The cooperated reactions achieve the complete degradation and highly efficient mineralization of DDVP and AZX.
文摘In two-dimensional(2D)materials,due to weak interlayer van der Waals(vdW)interaction,the crystal structure can be tuned through the control of interlayer stacking with a rather low increase in energy.Whereas most previous work has focused on the electronic and optical properties associated with the vdW stacking,the recent discovery of magnetism in 2D materials extends this research area to magnetic properties.CrI3 and CrBr3 are two isostructural ferromagnetic 2D materials,which maintain out-of-plane ferromagnetism down to the monolayer limit.However,as confirmed through recent experiments based on mechanically exfoliated samples,CrI3 bilayers exhibit interlayer antiferromagnetism,while CrBr3 bilayers exhibit interlayer ferromagnetism.Such a striking difference in the magnetic properties between bilayers of CrI3 and CrBr3 prompts a thorough investigation of the mechanisms governing the interlayer magnetic coupling.
基金supported by the National Key Research Program of China(Grant No.2020YFA0309100)the National Natural Science Foundation of China(Grant Nos.11991062,12074075,12074073,12074071,and 11904052)+1 种基金the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the Shanghai Municipal Natural Science Foundation(Grant Nos.20501130600,22ZR1407400,and 22ZR1408100).
文摘We report a significantly enhanced anomalous Hall effect(AHE)of Pt on antiferromagnetic insulator thin film(3-unit-cell La_(0.7)Sr_(0.3)MnO_(3),abbreviated as LSMO),which is one order of magnitude larger than that of Pt on other ferromagnetic(e.g.Y_(3)Fe_(5)O_(12))and antiferromagnetic(e.g.Cr_(2)O_(3))insulator thin films.Our experiments demonstrate that the antiferromagnetic La_(0.7)Sr_(0.3)MnO_(3)with fully compensated surface suppresses the positive anomalous Hall resistivity induced by the magnetic proximity effect and facilitates the negative anomalous Hall resistivity induced by the spin Hall effect.By changing the substrate’s temperature during Pt deposition,we observed that the diffusion of Mn atoms into Pt layer can further enhance the AHE.The anomalous Hall resistivity increases with increasing temperature and persists even well above the Neel temperature(T_(N))of LSMO.The Monte Carlo simulations manifest that the unusual rise of anomalous Hall resistivity above T_(N)originates from the thermal induced magnetization in the antiferromagnetic insulator.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0300702)Shanghai Municipal Natural Science Foundation,China(Grant Nos.19ZR1402800,18JC1411400,18ZR1403200,and 17ZR1442600)+1 种基金the Program of Shanghai Academic Research Leader,China(Grant Nos.18XD1400600 and 17XD1400400)the China Postdoctoral Science Foundation(Grant Nos.2016M601488 and 2017T100265)
文摘We reported a study of tunnel magnetoresistance(TMR)effect in single manganite nanowire via the combination of magnetotransport and magnetic force microscopy imaging.TMR value up to 290%has been observed in single(La1-yPry)1-x CaxMnO3 nanowires with varying width.We find that the TMR effect can be explained in the scenario of opening and blockade of conducting channels from inherent magnetic domain evolutions.Our findings provide a new route to fabricate TMR junctions and point towards future improvements in complex oxide-based TMR spintronics.
文摘A number of recent studies have demonstrated that electrochemical technologies, including electroreduction （ER）, electrocoagulation （EC）, and electrodialysis （ED）, are effbctive in nitrate elimination in wastewater due to their high reactivity. To obtain the maximal elimination efficiency and current efficiency, many researchers have conducted experiments to investigate the optimal conditions （i.e., potential, cun＇ent density, pH value, plate distance, initial nitrate concentration, electrolyte, and other factors） tbr nitrate elimination. The mechanism of ER, EC and ED for nitrate removal has been fully elucidated. The ER mechanism of nitrate undergoes electron transfer and hydrogenation reduction. The EC pathways of nitrate removal include reduction, coagulation and flotation. The ED pathways of nitrate include redox reaction and dialysis. Although the electrochemical technology can remove nitrate from wastewater efficiently, many problems （such as relatively low selectivity toward nitrogen, sludge production and brine generation） still hinder electrochemical treatment implementa- tion. This paper critically presents an overview of the current state-of-the-art of electrochemical denitrification to enhance the removal efficiency and overcome the shortages, and will significantly improve the understanding of the detailed processes and mechanisms of nitrate removal by electrochemical treatment and provide useful information to scientific research and actual practice.
基金supported by the National Key Research Program of China(Grant No.2016YFA0300702)the National Basic Research Program of China(Grant No.2014CB921104)+5 种基金the Shanghai Municipal Natural Science Foundation(Grant Nos.18JC1411400,18ZR1403200,and 17ZR1442400)the National Natural Science Foundation of China(Grant No.U1530402)the National Natural Science Foundation of China(Grant No.11674188)China Postdoctoral Science Foundation(Grant No.2017M610221)Shanghai Sailing Program(Grant No.17YF1429000)the National Postdoctoral Program for Innovative Talents(Grant No.BX201600036)
文摘Numerous exotic properties have been discovered in Dirac Semimetals(DSMs) and Weyl Semimetals(WSMs). In a given DSM/WSM, the Dirac/Weyl nodes usually coexist with other bulk states, making their respective contribution elusive. In this work, we distinguish the role of bulk states from the tilted Dirac nodes on the transport properties in DSMs. Specifically, we applied pressure to a type-II DSM material, PtTe2, and studied its pressure modified electronic and lattice structure systematically by using in situ transport measurements and X-ray diffraction(XRD). A pressure-induced transition at about 20 GPa is revealed in the transport properties, while the layered lattice structure is robust against pressure as illustrated in XRD measurement results.Density functional theory(DFT) calculations suggest that this is originated from the Lifshitz transition in the bulk states. Our findings provide evidence to identify the bulk states' influence on transport from the topologically-protected DSM states in the DSM material.
基金the National Natural Science Foundation of China(Grant No.21777009)Beijing Natural Science Foundation(Grant No.8182031)Major Science and Technology Program for Water Pollution Control and Treatment(Grant No.2018ZX07109).
文摘Photocatalytic hydrogen production synergized with the oxidation of pollutants is an environmentally friendly and economical approach to generate clean energy and remove the pollution from environment.In this study,photocatalytic hydrogen production cooperating with 2,4,6-trichlorophenol(2,4,6-TCP)degradation have been reinforced by introducing an ultrasonic atomization.The degradation of 2,4,6-TCP in a mist of three photocatalysts(g-C3N4,TiO2,and Bi2O3)generated by ultrasonic atomization was performed under 254 nm ultraviolet(UV254)light irradiation.The results showed that,under UV254 irradiation,three different photocatalysts(g-C3N4,TiO2,and Bi2O3)all accelerated both hydrogen production and 2,4,6-TCP degradation.Additionally,2,4,6-TCP degradation and photocatalytic hydrogen production exhibited an obvious synergistic effect,since 2,4,6-TCP has a strong tendency to react with photo-generated holes and their second radicals so as to inhibit the recombination of carriers,and thus improved the efficiency of hydrogen production simultaneously.Moreover,by introducing ultrasonic atomization,the atomized droplets acted as micro-photocatalytic units to replace the macrophotocatalytic reaction reactor.Therefore,the mass transfer distance for free radicals was restricted and the utilization of light energy by photocatalysts was increased.Further,the reaction efficiency was improved.The results reveal environmentally friendly and economical potential of hydrogen production by photocatalytic degradation of 2,4,6-TCP in atomized droplets.
基金the National Key Research and Development Program of China(Grant No.2016YFA0300702)the Shanghai Municipal Natural Science Foundation(Grant Nos.19ZR1402800,18JC1411400,18ZR1403200,and 17ZR1442600)+1 种基金the Program of Shanghai Academic Research Leader(Grant Nos.18XD1400600,and 17XD1400400)the China Postdoctoral Science Foundation(Grant Nos.2016M601488,and 2017T100265)。
文摘Complex oxides have rich functionalities and advantages for future technologies.In many systems,quenched disorder often holds the key to determine their physical properties,and these properties can be further tuned by chemical doping.However,understanding the role of quenched disorder is complicated because chemical doping simultaneously alters other physical variables such as local lattice distortions and electronic and magnetic environments.Here,we show that spatial confinement is an effective approach to tuning the level of quenched disorder in a complex-oxide system while leaving other physical variables largely undisturbed.Through the confinement of a manganite system down to quasi-one-dimensional nanowires,we observed that the nature of its metal-insulator phase transition exhibits a crossover from a discontinuous to a continuous characteristic,in close accordance with quenched disorder theories.We argue that the quenched disorder,finite size,and surface effects all contribute to our experimental observations.Noticeably,with reduced nanowire width,the magnetoresistance shows substantial enhancement at low temperatures.Our findings offer new insight into experimentally tuning the quenched disorder effect to achieve novel functionalities at reduced dimensions.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFA0300702)the National Basic Research Program of China(973 Program)(Grant No.2014CB921104)+1 种基金the Program of Shanghai Academic Research Leader(Grant No.17XD1400400)the National Natural Science Foundation of China(Grant No.11504053)
文摘Light,acting as an external stimulus to induce various intriguing phenomena ranging from photovoltaics to photoinduced catalysis,exerts prominent effects in strongly correlated systems.It would be of particular interest to investigate photon-induced emerging phenomena in spatially confined strongly correlated systems,which are important for applications of these materials in future electronic devices.Colossal magnetoresistive manganites materials offer an ideal platform for such study due to their sensitivity to photo-excitation.Here,we fabricated 900 nm wide La_(0.325)Pr_(0.3)Ca_(0.375)Mn O_3strips,whose width is comparable to the size of the electronic phase separation(EPS)domains in this system.We observed the photoinduced critical fluctuations in the strips,where abrupt resistivity jumps occurred upon photoinduced phase transition depending sensitively on the light intensity.Based on the microscopic views of the EPS domains under photoexcitation,we conclude that such photo-induced resistivity fluctuations originate from the photoinduced phase fluctuations of individual EPS domains when their size becomes comparable to the strip width.
文摘Manganese selenide （MnSe） possesses unique magnetic properties as an important magnetic semiconductor, but the synthesis and properties of MnSe nanocrystals are less developed compared to other semiconductor nanocrystals because of the inability to obtain high-quality MnSe, especially in the metastable wurtzite structure. Here, we have successfully fabricated wurtzite MnSe nanocrystals via a colloidal approach which affords uniform crystal sizes and tailored shapes. The selective binding strength of the amine surfactant is the determining factor in shape-control and shape-evolution. Bullet-shapes could be transformed into shuttle-shapes if part of the oleylamine in the reaction solution was replaced by trioctylamine, and tetrapod-shaped nanocrystals could be formed in trioctylamine systems. The three-dimensional （3D） structure of the bullet-shaped nanorods has been demonstrated by the advanced transmission electron microscope （TEM） 3D-tomography technology. High-resolution TEM （HRTEM） and electron energy-loss spectroscopy （EELS） show that planar-defect structures such as stacking faults and twinning along the [001] direction arise during the growth of bullet-shapes. On the basis of careful HRTEM observations, we propose a ＂quadra-twin core＂ growth mechanism for the formation of wurtzite MnSe nanotetrapods. Furthermore, the wurtzite MnSe nanocrystals show low- temperature surface spin-glass behavior due to their noncompensated surface spins and the blocking temperatures increase from 8.4 K to 18.5 K with increasing surface area/volume ratio of the nanocrystals. Our results provide a systematic study of wurtzite MnSe nanocrystals.
基金supported by the National Key Research and Development Program of China(2022YFA1403300 and 2020YFA0309100)the National Natural Science Foundation of China(11991060,12074075,12074073,12074071,12074080,and 12274088)+3 种基金the Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)the Shanghai Municipal Natural Science Foundation(20501130600,22ZR1408100,22ZR1407400,and 23ZR1407200)support from the National Key Research and Development Program of China(2021YFA1400503 and 2021YFA1400202)the National Natural Science Foundation of China(12125403,11874123,and 12221004).
文摘In correlated oxides,collaborative manipulation on light intensity,wavelength,pulse duration and polarization has yielded many exotic discoveries,such as phase transitions and novel quantum states.In view of potential optoelectronic applications,tailoring long-lived static properties by light-induced effects is highly desirable.So far,the polarization state of light has rarely been reported as a control parameter for this purpose.Here,we report polarization-dependent metal-to-insulator transition(MIT)in phaseseparated manganite thin films,introducing a new degree of freedom to control static MIT.Specifically,we observed giant photoinduced resistance jumps with striking features:(1)a single resistance jump occurs upon a linearly polarized light incident with a chosen polarization angle,and a second resistance jump occurs when the polarization angle changes;(2)the amplitude of the second resistance jump depends sensitively on the actual change of the polarization angles.Linear transmittance measurements reveal that the origin of the above phenomena is closely related to the coexistence of anisotropic micro-domains.Our results represent a first step to utilize light polarization as an active knob to manipulate static phase transitions,pointing towards new pathways for nonvolatile optoelectronic devices and sensors.
