The electro-physical properties of thin layers of rhenium chalcogenides＇ alloys, their dynamical and static ampere-voltaic characteristics were investigated. During the investigation of static and dynamical ampere-vo...The electro-physical properties of thin layers of rhenium chalcogenides＇ alloys, their dynamical and static ampere-voltaic characteristics were investigated. During the investigation of static and dynamical ampere-voltaic characteristics of rectifying contact of aluminium and rhenium chalcogenides＇ alloys the switching effects were found.展开更多
Chalcogenide perovskites(CPs)based on zirconium(Zr)and hafnium(Hf)are becoming increasingly attractive as a new class of materials for next-generation solar cells.CPs with the ABX_(3) structure stand out due to their ...Chalcogenide perovskites(CPs)based on zirconium(Zr)and hafnium(Hf)are becoming increasingly attractive as a new class of materials for next-generation solar cells.CPs with the ABX_(3) structure stand out due to their attractive optical and electrical properties,such as efficient light absorption,direct bandgaps in the range of 1.1–2.1 eV,and remarkable defect tolerance,making them a compelling alternative to hybrid and double perovskites for solar energy conversion.Although theoretical studies have progressed rapidly,experimental verification still faces challenges such as the high synthesis temperatures required(>900℃),particularly in producing high-quality,phase-pure thin films and scalable solution-based processes.In this review,we aim to provide a comprehensive overview of the progress and remaining obstacles in advancing CP-based materials and devices.First,we describe the structure and composition as well as the different CPs in which the B site is occupied by Zr and Hf.Second,we summarize the methods used and the challenges that researchers face in producing an effective device.We highlight the main features that make CPs a preferred option for photovoltaic and other applications.Third,we look at the progress made in simulating solar cells that can achieve a power conversion efficiency(PCE)of over 30%using SCAPS-1D software.In the end,challenges and future research directions toward the development of CP materials and devices are provided.Overall,this review will serve as a valuable resource for researchers in selecting suitable strategies to achieve high-performance optoelectronic devices.展开更多
Two-dimensional(2D)transition metal chalcogenides(TMC)and their heterostructures are appealing as building blocks in a wide range of electronic and optoelectronic devices,particularly futuristic memristive and synapti...Two-dimensional(2D)transition metal chalcogenides(TMC)and their heterostructures are appealing as building blocks in a wide range of electronic and optoelectronic devices,particularly futuristic memristive and synaptic devices for brain-inspired neuromorphic computing systems.The distinct properties such as high durability,electrical and optical tunability,clean surface,flexibility,and LEGO-staking capability enable simple fabrication with high integration density,energy-efficient operation,and high scalability.This review provides a thorough examination of high-performance memristors based on 2D TMCs for neuromorphic computing applications,including the promise of 2D TMC materials and heterostructures,as well as the state-of-the-art demonstration of memristive devices.The challenges and future prospects for the development of these emerging materials and devices are also discussed.The purpose of this review is to provide an outlook on the fabrication and characterization of neuromorphic memristors based on 2D TMCs.展开更多
Transition metal chalcogenides(TMCs)and TMCs-based nanocomposites have attracted extensive attention due to their versatile material species,low cost,and rich physical and chemical characteristics.As anode materials o...Transition metal chalcogenides(TMCs)and TMCs-based nanocomposites have attracted extensive attention due to their versatile material species,low cost,and rich physical and chemical characteristics.As anode materials of lithium-ion capacitors(LICs),TMCs have exhibited high theoretical capacities and pseudocapacitance storage mechanism.However,there are many intrinsic challenges,such as low electrical conductivity,repeatedly high-volume changes and sluggish ionic diffusion kinetics.Hence,many traditional and unconventional techniques have been reported to solve these critical problems,and many innovative strategies are also used to prepare high quality anode materials for LICs.In this mini review,a detailed family member list and comparison of TMCs in the field of lithium-ion capacitors have been summarized firstly.Then,many rectification stratagems and recent researches of TMCs have been exhibited and discussed.In the end,as an outcome of these discussions,some further challenges and perspectives are envisioned to promote the application of TMCs materials for lithium-ion c apacitors.展开更多
Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)converts CO_(2)into valuable chemical fuels,which can effectively alleviate global warming and energy crisis.However,limited by its slow reaction rate and low product...Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)converts CO_(2)into valuable chemical fuels,which can effectively alleviate global warming and energy crisis.However,limited by its slow reaction rate and low product selectivity,it is urgent to design efficient,cheap,safe,and highly selective CO_(2)RR electrocatalysts.Owing to the advantages of adjustable electronic structure,abundant active sites,low cost,environmental friendliness and excellent electrochemical performance,bimetallic chalcogenides have aroused great interest.Here,we briefly summarized different bimetallic oxides and sulfides for electrocatalytic CO_(2)RR in the past five years.In addition,different hybridizations formed between metal atoms,including intermetallic compounds,heterostructures and metal doping,were generalized.Their positive effects on CO_(2)RR catalytic selectivity and activity were deeply uncovered.Besides,we also put forward some views about the future research directions and perspectives in CO_(2)RR field.This review aims to provide a reference for the rational design of bimetallic chalcogenides towards electrocatalytic CO_(2)reduction.展开更多
Wearable smart sensors are considered to be the new generation of personal portable devices for health monitoring.By attaching to the skin surface,these sensors are closely related to body signals(such as heart rate,b...Wearable smart sensors are considered to be the new generation of personal portable devices for health monitoring.By attaching to the skin surface,these sensors are closely related to body signals(such as heart rate,blood oxygen saturation,breath markers,etc.)and ambient signals(such as ultraviolet radiation,inflammable and explosive,toxic and harmful gases),thus providing new opportunities for human activity monitoring and personal telemedicine care.Here we focus on photodetectors and gas sensors built from metal chalcogenide,which have made great progress in recent years.Firstly,we present an overview of healthcare applications based on photodetectors and gas sensors,and discuss the requirement associated with these applications in detail.We then discuss advantages and properties of solution-processable metal chalcogenides,followed by some recent achievements in health monitoring with photodetectors and gas sensors based on metal chalcogenides.Last we present further research directions and challenges to develop an integrated wearable platform for monitoring human activity and personal healthcare.展开更多
Frustrated quantum magnets are expected to host many exotic quantum spin states like quantum spin liquid（QSL）, and have attracted numerous interest in modern condensed matter physics. The discovery of the triangular...Frustrated quantum magnets are expected to host many exotic quantum spin states like quantum spin liquid（QSL）, and have attracted numerous interest in modern condensed matter physics. The discovery of the triangular lattice spin liquid candidate YbMgGaO_4 stimulated an increasing attention on the rare-earth-based frustrated magnets with strong spin-orbit coupling. Here we report the synthesis and characterization of a large family of rare-earth chalcogenides AReCh_2（A = alkali or monovalent ions, Re = rare earth, Ch = O,S,Se）. The family compounds share the same structure（R3 m） as YbMgGaO_4,and antiferromagnetically coupled rare-earth ions form perfect triangular layers that are well separated along the c-axis. Specific heat and magnetic susceptibility measurements on NaYbO_2,NaYbS_2 and NaYbSe_2 single crystals and polycrystals, reveal no structural or magnetic transition down to 50 mK. The family, having the simplest structure and chemical formula among the known QSL candidates, removes the issue on possible exchange disorders in YbMgGaO_4. More excitingly, the rich diversity of the family members allows tunable charge gaps, variable exchange coupling, and many other advantages.This makes the family an ideal platform for fundamental research of QSLs and its promising applications.展开更多
Recently,non-centrosymmetric(NCS)Hg-based chalcogenides have garnered significant interest due to their strong second-harmonic-generation intensities(deff),making them attractive candidates for infrared nonlinear opti...Recently,non-centrosymmetric(NCS)Hg-based chalcogenides have garnered significant interest due to their strong second-harmonic-generation intensities(deff),making them attractive candidates for infrared nonlinear optical(IR-NLO)application.However,achieving both wide band gaps(Eg)and large phasematched deffsimultaneously in these materials remains a challenge due to their inherent constraints on each other.In this research,we have successfully obtained two quaternary NCS Hg-based chalcogenides,Rb2HgGe_(3)S_(8)and Cs_(2)HgGe_(3)S_(8),by implementing a bandgap engineering strategy that involves alkali metal introduction and Hg/Ge ratio regulation.Both compounds consist of 2D[Hg Ge_(3)S_(8)]_(2)–anionic layers made of 1D[HgGeS_(6)]^(6–)chains and dimeric[Ge_(2)S_(6)]_(4–)polyhedra arranged alternately,and the charge-balanced Rb+/Cs+cations located between these layers.Remarkably,Rb_(2)HgGe_(3)S_(8)and Cs_(2)HgGe_(3)S_(8)exhibit overall properties required for promising IR-NLO materials,including sufficient PM deff(0.55–0.70×AgGaS_(2)@20_(5)0 nm),large Eg(3.27–3.41 e V),giant laser-induced damage thresholds(17.4–19.7×AgGaS_(2)@1064 nm),broad optical transmission intervals(0.32–17.5μm),and suitable theoretical birefringence(0.069–0.086@2050 nm).Furthermore,in-depth theoretical analysis reveals that the exceptional IRNLO performance is attributed to the synergy effects of distorted[HgS_(4)]and[GeS_(4)]tetrahedra.Our study provides a useful strategy for enhancing the Eg and advancing Hg-based IR-NLO materials,which is expected to extended and implemented in other chalcogenide systems.展开更多
A complex longitudinal magnetoresistance （MR//） effect in the non-stoichiometric silver chaJcogenides （include the silver selenide and telluride） has been found, however the mechanism for the MR// effect is not cl...A complex longitudinal magnetoresistance （MR//） effect in the non-stoichiometric silver chaJcogenides （include the silver selenide and telluride） has been found, however the mechanism for the MR// effect is not clear now. In this work, a new random resistor network for MR// effect is proposed based on the experimental observation. The network is constructed from six-terminal resistor units and the mobility of carries within the network has a Gaussian distribution. Considering the non-zero transverse-longitudinal coupling in materials, the resistance matrix of the six- terminal resistor unit is modified. It is found that the material has the ＂chiral＂ transverse-longitudinal couplings, which is suggested a main reason for the complex MR//effect. The model predictions are compared with the experimental results. A three dimension （3D） visualization of current flow within the network demonstrates the ＂current jets＂ phenomenon in the thickness of materials dearly.展开更多
Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electr...Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu_(2)TlX_(2)(X = Se, Te), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu_(2)TlSe_(2) to a semimetal in Cu_(2)TlTe_(2), suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin–orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin–orbit coupling.展开更多
Two ternary europium chalcogenides, Eu1-xGa2Te4（x ≈ 0.19）（1） and EuY2Se4（2）, have been synthesized by a facile solid-state route using boron as the reducing reagent. Eu1-xGa2Te4 crystallizes in the tetragonal s...Two ternary europium chalcogenides, Eu1-xGa2Te4（x ≈ 0.19）（1） and EuY2Se4（2）, have been synthesized by a facile solid-state route using boron as the reducing reagent. Eu1-xGa2Te4 crystallizes in the tetragonal space group I4/mcm with a = 8.2880（9）, c = 6.7439（12） A, V = 463.24（13） A^3, and Z = 2. EuY2Se4 crystallizes in the orthorhombic space group Pnma with a = 12.4726（16）, b = 4.1204（6）, c = 14.849（2） A, V = 763.11（19） A^3, and Z = 4. Eu1-xGa2Te4 belongs to the Tl Se-type 3D closed structure, while EuY2Se4 adopts the CaFe2O4-type 3D channel structure. The optical band gap of Eu1-xGa2Te4 is determined to be 0.48 Ev. Electronic structures of 1 and 2 are calculated using TB-LMTO software.展开更多
Non-layered two-dimensional(2D)materials have sparked much interest recently due to their atomic thickness,large surface area,thickness-and facet-dependent properties.Currently,these materials are mainly grown from we...Non-layered two-dimensional(2D)materials have sparked much interest recently due to their atomic thickness,large surface area,thickness-and facet-dependent properties.Currently,these materials are mainly grown from wet-chemistry methods but suffer from small size,low quality,and multi-facets,which is a major challenge hindering their facet-dependent property studies and applications.Here,we report the facet-engineered growth(FEG)of non-layered 2D manganese chalcogenides(MnX,X=S,Se,Te)based on the chemical vapor deposition method.The as-grown samples exhibit large-area surfaces of single facet,high-crystallinity,and ordered domain orientation.As a proof-of-concept,we show the facet-dependent electrocatalytic property of non-layered 2D MnSe,proving they are ideal candidates for fundamental research.Furthermore,we elucidate the underlying mechanism of FEG during the vapor growth process by the interfacial energy derived nucleation models.The method developed in this work provides new opportunities for regulating and designing the structure of 2D materials.展开更多
Band gap anomaly is a well-known issue in lead chalcogenides PbX （X = S, Se, Te, Po）. Combining ab initio calculations and tight-binding （TB） method, we have studied the band evolution in PbX, and found that the b...Band gap anomaly is a well-known issue in lead chalcogenides PbX （X = S, Se, Te, Po）. Combining ab initio calculations and tight-binding （TB） method, we have studied the band evolution in PbX, and found that the band gap anomaly in PbTe is mainly related to the high on-site energy of Te 5s orbital and the large s-p hopping originated from the irregular extended distribution of Te 5s electrons. Furthermore, our calculations show that PbPo is an indirect band gap （6.5 meV） semiconductor with band inversion at L point, which clearly indicates that PbPo is a topological crystalline insulator （TCI）. The calculated mirror Chern number and surface states double confirm this conclusion.展开更多
文摘The electro-physical properties of thin layers of rhenium chalcogenides＇ alloys, their dynamical and static ampere-voltaic characteristics were investigated. During the investigation of static and dynamical ampere-voltaic characteristics of rectifying contact of aluminium and rhenium chalcogenides＇ alloys the switching effects were found.
基金the“Initiative on Energy Research”,founded by the University Mohammed VI Polytechnic,for the financial support through the project“Toward efficient,stable,environmentally friendly,and scalable Perovskite Solar Cells”the financial support from DAAD and BMZ through the WE-AFRICA project+1 种基金the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Early Career Program,under Award No.DOE DESC0025350the National Academies of Sciences,Engineering,and Medicine for their support through the U.S.-Africa Frontiers Fellowship。
文摘Chalcogenide perovskites(CPs)based on zirconium(Zr)and hafnium(Hf)are becoming increasingly attractive as a new class of materials for next-generation solar cells.CPs with the ABX_(3) structure stand out due to their attractive optical and electrical properties,such as efficient light absorption,direct bandgaps in the range of 1.1–2.1 eV,and remarkable defect tolerance,making them a compelling alternative to hybrid and double perovskites for solar energy conversion.Although theoretical studies have progressed rapidly,experimental verification still faces challenges such as the high synthesis temperatures required(>900℃),particularly in producing high-quality,phase-pure thin films and scalable solution-based processes.In this review,we aim to provide a comprehensive overview of the progress and remaining obstacles in advancing CP-based materials and devices.First,we describe the structure and composition as well as the different CPs in which the B site is occupied by Zr and Hf.Second,we summarize the methods used and the challenges that researchers face in producing an effective device.We highlight the main features that make CPs a preferred option for photovoltaic and other applications.Third,we look at the progress made in simulating solar cells that can achieve a power conversion efficiency(PCE)of over 30%using SCAPS-1D software.In the end,challenges and future research directions toward the development of CP materials and devices are provided.Overall,this review will serve as a valuable resource for researchers in selecting suitable strategies to achieve high-performance optoelectronic devices.
基金supported by the Characterization platform for advanced materials funded by the Korea Research Institute of Standards and Science(KRISS-2021-GP2021-0011)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government MSIT(2021M3D1A20396541).
文摘Two-dimensional(2D)transition metal chalcogenides(TMC)and their heterostructures are appealing as building blocks in a wide range of electronic and optoelectronic devices,particularly futuristic memristive and synaptic devices for brain-inspired neuromorphic computing systems.The distinct properties such as high durability,electrical and optical tunability,clean surface,flexibility,and LEGO-staking capability enable simple fabrication with high integration density,energy-efficient operation,and high scalability.This review provides a thorough examination of high-performance memristors based on 2D TMCs for neuromorphic computing applications,including the promise of 2D TMC materials and heterostructures,as well as the state-of-the-art demonstration of memristive devices.The challenges and future prospects for the development of these emerging materials and devices are also discussed.The purpose of this review is to provide an outlook on the fabrication and characterization of neuromorphic memristors based on 2D TMCs.
基金financially supported by the National Natural Science Foundation of China(No.51907193)the Key Research Program of Frontier Sciences,CAS(No.ZDBS-LYJSC047)+1 种基金the Youth Innovation Promotion Association CAS(No.2020145)Dalian National Laboratory for Clean Energy Cooperation Fund,the CAS(No.DNL201915)。
文摘Transition metal chalcogenides(TMCs)and TMCs-based nanocomposites have attracted extensive attention due to their versatile material species,low cost,and rich physical and chemical characteristics.As anode materials of lithium-ion capacitors(LICs),TMCs have exhibited high theoretical capacities and pseudocapacitance storage mechanism.However,there are many intrinsic challenges,such as low electrical conductivity,repeatedly high-volume changes and sluggish ionic diffusion kinetics.Hence,many traditional and unconventional techniques have been reported to solve these critical problems,and many innovative strategies are also used to prepare high quality anode materials for LICs.In this mini review,a detailed family member list and comparison of TMCs in the field of lithium-ion capacitors have been summarized firstly.Then,many rectification stratagems and recent researches of TMCs have been exhibited and discussed.In the end,as an outcome of these discussions,some further challenges and perspectives are envisioned to promote the application of TMCs materials for lithium-ion c apacitors.
基金financially supported by Hunan Provincial Science and Technology Plan Project(Nos.2017TP1001 and 2017JJ2347)Changsha Science and Technology Plan(No.kq1801079)+1 种基金Hunan Key Laboratory of Two-Dimensional Materials(No.2018TP1010)the National Natural Science Foundation of China(No.21776317)。
文摘Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)converts CO_(2)into valuable chemical fuels,which can effectively alleviate global warming and energy crisis.However,limited by its slow reaction rate and low product selectivity,it is urgent to design efficient,cheap,safe,and highly selective CO_(2)RR electrocatalysts.Owing to the advantages of adjustable electronic structure,abundant active sites,low cost,environmental friendliness and excellent electrochemical performance,bimetallic chalcogenides have aroused great interest.Here,we briefly summarized different bimetallic oxides and sulfides for electrocatalytic CO_(2)RR in the past five years.In addition,different hybridizations formed between metal atoms,including intermetallic compounds,heterostructures and metal doping,were generalized.Their positive effects on CO_(2)RR catalytic selectivity and activity were deeply uncovered.Besides,we also put forward some views about the future research directions and perspectives in CO_(2)RR field.This review aims to provide a reference for the rational design of bimetallic chalcogenides towards electrocatalytic CO_(2)reduction.
基金supported by National Natural Science Foundation of China (61861136004)the National Key R&D Program of China (2016YFB0402705)+1 种基金the Innovation Fund of WNLOProgram for HUST Academic Frontier Youth Team (2018QYTD06)
文摘Wearable smart sensors are considered to be the new generation of personal portable devices for health monitoring.By attaching to the skin surface,these sensors are closely related to body signals(such as heart rate,blood oxygen saturation,breath markers,etc.)and ambient signals(such as ultraviolet radiation,inflammable and explosive,toxic and harmful gases),thus providing new opportunities for human activity monitoring and personal telemedicine care.Here we focus on photodetectors and gas sensors built from metal chalcogenide,which have made great progress in recent years.Firstly,we present an overview of healthcare applications based on photodetectors and gas sensors,and discuss the requirement associated with these applications in detail.We then discuss advantages and properties of solution-processable metal chalcogenides,followed by some recent achievements in health monitoring with photodetectors and gas sensors based on metal chalcogenides.Last we present further research directions and challenges to develop an integrated wearable platform for monitoring human activity and personal healthcare.
基金Supported by the Ministry of Science and Technology of China under Grant Nos 2016YFA0300504,2017YFA0302904 and 2016YFA0301001the Natural Science Foundation of China under Grant Nos 11774419,11474357,11822412,11774423 and 11574394
文摘Frustrated quantum magnets are expected to host many exotic quantum spin states like quantum spin liquid（QSL）, and have attracted numerous interest in modern condensed matter physics. The discovery of the triangular lattice spin liquid candidate YbMgGaO_4 stimulated an increasing attention on the rare-earth-based frustrated magnets with strong spin-orbit coupling. Here we report the synthesis and characterization of a large family of rare-earth chalcogenides AReCh_2（A = alkali or monovalent ions, Re = rare earth, Ch = O,S,Se）. The family compounds share the same structure（R3 m） as YbMgGaO_4,and antiferromagnetically coupled rare-earth ions form perfect triangular layers that are well separated along the c-axis. Specific heat and magnetic susceptibility measurements on NaYbO_2,NaYbS_2 and NaYbSe_2 single crystals and polycrystals, reveal no structural or magnetic transition down to 50 mK. The family, having the simplest structure and chemical formula among the known QSL candidates, removes the issue on possible exchange disorders in YbMgGaO_4. More excitingly, the rich diversity of the family members allows tunable charge gaps, variable exchange coupling, and many other advantages.This makes the family an ideal platform for fundamental research of QSLs and its promising applications.
基金supported by the National Natural Science Foundation of China(Nos.22175175 and 22193043)Natural Science Foundation of Fujian Province(Nos.2022L3092 and 2023H0041)+1 种基金Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(No.2021ZR118)the Youth Innovation Promotion Association CAS(No.2022303)。
文摘Recently,non-centrosymmetric(NCS)Hg-based chalcogenides have garnered significant interest due to their strong second-harmonic-generation intensities(deff),making them attractive candidates for infrared nonlinear optical(IR-NLO)application.However,achieving both wide band gaps(Eg)and large phasematched deffsimultaneously in these materials remains a challenge due to their inherent constraints on each other.In this research,we have successfully obtained two quaternary NCS Hg-based chalcogenides,Rb2HgGe_(3)S_(8)and Cs_(2)HgGe_(3)S_(8),by implementing a bandgap engineering strategy that involves alkali metal introduction and Hg/Ge ratio regulation.Both compounds consist of 2D[Hg Ge_(3)S_(8)]_(2)–anionic layers made of 1D[HgGeS_(6)]^(6–)chains and dimeric[Ge_(2)S_(6)]_(4–)polyhedra arranged alternately,and the charge-balanced Rb+/Cs+cations located between these layers.Remarkably,Rb_(2)HgGe_(3)S_(8)and Cs_(2)HgGe_(3)S_(8)exhibit overall properties required for promising IR-NLO materials,including sufficient PM deff(0.55–0.70×AgGaS_(2)@20_(5)0 nm),large Eg(3.27–3.41 e V),giant laser-induced damage thresholds(17.4–19.7×AgGaS_(2)@1064 nm),broad optical transmission intervals(0.32–17.5μm),and suitable theoretical birefringence(0.069–0.086@2050 nm).Furthermore,in-depth theoretical analysis reveals that the exceptional IRNLO performance is attributed to the synergy effects of distorted[HgS_(4)]and[GeS_(4)]tetrahedra.Our study provides a useful strategy for enhancing the Eg and advancing Hg-based IR-NLO materials,which is expected to extended and implemented in other chalcogenide systems.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 50872038 and 10675048
文摘A complex longitudinal magnetoresistance （MR//） effect in the non-stoichiometric silver chaJcogenides （include the silver selenide and telluride） has been found, however the mechanism for the MR// effect is not clear now. In this work, a new random resistor network for MR// effect is proposed based on the experimental observation. The network is constructed from six-terminal resistor units and the mobility of carries within the network has a Gaussian distribution. Considering the non-zero transverse-longitudinal coupling in materials, the resistance matrix of the six- terminal resistor unit is modified. It is found that the material has the ＂chiral＂ transverse-longitudinal couplings, which is suggested a main reason for the complex MR//effect. The model predictions are compared with the experimental results. A three dimension （3D） visualization of current flow within the network demonstrates the ＂current jets＂ phenomenon in the thickness of materials dearly.
基金supported by the National Natural Science Foundation of China (Grant No. 11774190)。
文摘Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu_(2)TlX_(2)(X = Se, Te), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu_(2)TlSe_(2) to a semimetal in Cu_(2)TlTe_(2), suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin–orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin–orbit coupling.
基金supported by NNSFC(21771159)NSF of Yangzhou(YZ2016122)State Key Lab of Structural Chemistry Fund(20150009)
文摘Two ternary europium chalcogenides, Eu1-xGa2Te4（x ≈ 0.19）（1） and EuY2Se4（2）, have been synthesized by a facile solid-state route using boron as the reducing reagent. Eu1-xGa2Te4 crystallizes in the tetragonal space group I4/mcm with a = 8.2880（9）, c = 6.7439（12） A, V = 463.24（13） A^3, and Z = 2. EuY2Se4 crystallizes in the orthorhombic space group Pnma with a = 12.4726（16）, b = 4.1204（6）, c = 14.849（2） A, V = 763.11（19） A^3, and Z = 4. Eu1-xGa2Te4 belongs to the Tl Se-type 3D closed structure, while EuY2Se4 adopts the CaFe2O4-type 3D channel structure. The optical band gap of Eu1-xGa2Te4 is determined to be 0.48 Ev. Electronic structures of 1 and 2 are calculated using TB-LMTO software.
基金This work was supported by the National Science Fund for Distinguished Young Scholars(52125309)the National Natural Science Foundation of China(51991343,51920105002,and 52102179)+4 种基金Guangdong Basic and Applied Basic Research Foundation(2023A1515011752)Guangdong Innovative and Entrepreneurial Research Team Program(2017ZT07C341)Shenzhen Basic Research Project(JCYJ20200109144616617,JCYJ20220818101014029)Shuimu Tsinghua Scholar Program(2022SM092)China Postdoctoral Science Foundation(2021M691715)。
文摘Non-layered two-dimensional(2D)materials have sparked much interest recently due to their atomic thickness,large surface area,thickness-and facet-dependent properties.Currently,these materials are mainly grown from wet-chemistry methods but suffer from small size,low quality,and multi-facets,which is a major challenge hindering their facet-dependent property studies and applications.Here,we report the facet-engineered growth(FEG)of non-layered 2D manganese chalcogenides(MnX,X=S,Se,Te)based on the chemical vapor deposition method.The as-grown samples exhibit large-area surfaces of single facet,high-crystallinity,and ordered domain orientation.As a proof-of-concept,we show the facet-dependent electrocatalytic property of non-layered 2D MnSe,proving they are ideal candidates for fundamental research.Furthermore,we elucidate the underlying mechanism of FEG during the vapor growth process by the interfacial energy derived nucleation models.The method developed in this work provides new opportunities for regulating and designing the structure of 2D materials.
基金Project supported by the National Natural Science Foundation of China(Grant No.11204359)the National Basic Research Program of China(Grant No.2013CB921700)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB07020100)
文摘Band gap anomaly is a well-known issue in lead chalcogenides PbX （X = S, Se, Te, Po）. Combining ab initio calculations and tight-binding （TB） method, we have studied the band evolution in PbX, and found that the band gap anomaly in PbTe is mainly related to the high on-site energy of Te 5s orbital and the large s-p hopping originated from the irregular extended distribution of Te 5s electrons. Furthermore, our calculations show that PbPo is an indirect band gap （6.5 meV） semiconductor with band inversion at L point, which clearly indicates that PbPo is a topological crystalline insulator （TCI）. The calculated mirror Chern number and surface states double confirm this conclusion.
