Recently,transition-metal-based kagome metals have aroused much research interest as a novel platform to explore exotic topological quantum phenomena.Here we report on the synthesis,structure,and physical properties o...Recently,transition-metal-based kagome metals have aroused much research interest as a novel platform to explore exotic topological quantum phenomena.Here we report on the synthesis,structure,and physical properties of a bilayer kagome lattice compound V_(3)Sb_(2).The polycrystalline V_(3)Sb_(2) samples were synthesized by conventional solid-state-reaction method in a sealed quartz tube at temperatures below 850℃.Measurements of magnetic susceptibility and resistivity revealed consistently a density-wave-like transition at Tdw≈160 K with a large thermal hysteresis,even though some sample-dependent behaviors were observed presumably due to the different preparation conditions.Upon cooling through Tdw,no strong anomaly in lattice parameters and no indication of symmetry lowering were detected in powder x-ray diffraction measurements.This transition can be suppressed completely by applying hydrostatic pressures of about 1.8 GPa,around which no sign of superconductivity was observed down to 1.5 K.Specific-heat measurements revealed a relatively large Sommerfeld coefficientγ=18.5 mJ·mol^(-1)·K^(-2),confirming the metallic ground state with moderate electronic correlations.Density functional theory calculations indicate that V_(3)Sb_(2) shows a non-trivial topological crystalline property.Thus,our study makes V_(3)Sb_(2) a new candidate of metallic kagome compound to study the interplay between density-wave-order,nontrivial band topology,and possible superconductivity.展开更多
The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we...The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we report a titanium-based kagome metal CsTi_(3)Bi_(5)where titanium atoms form a kagome network,resembling its isostructural compound CsV_3Sb_5.Thermodynamic properties including the magnetization,resistance,and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi_(3)Bi_(5)and no signature of superconducting or charge density wave(CDW)transition anomaly down to 85 m K.Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level,consistent with the first-principles calculations.The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly.Compared to Cs V_(3)Sb_(5),the van Hove singularities are pushed far away above the Fermi level in CsTi_(3)Bi_(5),in line with the absence of CDW.Furthermore,the first-principles calculations identify the nontrivial Z_(2)topological properties for those bands crossing the Fermi level,accompanied by several local band inversions.Our results suppose CsTi_(3)Bi_(5)as a complementary platform to explore the superconductivity and nontrivial band topology.展开更多
Fig.1.(a)Structure of Co_(2)N_(2) dimer.(b)Structure;of Co_(2)N_(2) layer.The dashed black lines show the mirror symmetries.X,Y coordinates are defined according to the direction of the Co Co bond,and x,y are the glob...Fig.1.(a)Structure of Co_(2)N_(2) dimer.(b)Structure;of Co_(2)N_(2) layer.The dashed black lines show the mirror symmetries.X,Y coordinates are defined according to the direction of the Co Co bond,and x,y are the global coordinates in the conventional crystal structure.展开更多
In our most recently published article,[1]an important reference[2]predicting CsTi_(3)Bi_(5) is missing and should be added,along with Ref.[3](originally Ref.[28]),to the introduction section.
We predict that the square lattice layer formed by[Co_(2)N_(2)]_(2)-diamond-like units can host high-temperature superconductivity.The layer appears in the stable ternary cobalt nitride,Ba Co_(2)N_(2).The electronic p...We predict that the square lattice layer formed by[Co_(2)N_(2)]_(2)-diamond-like units can host high-temperature superconductivity.The layer appears in the stable ternary cobalt nitride,Ba Co_(2)N_(2).The electronic physics of the material stems from Co_(2)N_(2)layers where the dimerized Co pairs form a square lattice.The low energy physics near Fermi energy can be described by an effective two-orbital model.Without considering interlayer couplings,the two orbitals are effectively decoupled.This electronic structure satisfies the“gene”character proposed for unconventional high-temperature superconductors.We predict that the leading superconducting pairing instability is driven from an extended s-wave(s^(±))to a d-wave by hole doping,e.g.,in Ba_(1-x) K_(x) Co_(2)N_(2).This study provides a new platform to establish the superconducting mechanism of unconventional high-temperature superconductivity.展开更多
We show that the layered-structure BaCuS_(2) is a moderately correlated electron system in which the electronic structure of the CuS layer bears a resemblance to those in both cuprates and iron-based superconductors.T...We show that the layered-structure BaCuS_(2) is a moderately correlated electron system in which the electronic structure of the CuS layer bears a resemblance to those in both cuprates and iron-based superconductors.Theoretical calculations reveal that the in-plane d-p σ^(*)-bonding bands are isolated near the Fermi level.As the energy separation between the d and p orbitals are much smaller than those in cuprates and iron-based superconductors,BaCuS_(2) is expected to be moderately correlated.We suggest that this material is an ideal system to study the competitive/collaborative nature between two distinct superconducting pairing mechanisms,namely the conventional BCS electron-phonon interaction and the electron-electron correlation,which may be helpful to establish the elusive mechanism of unconventional high-temperature superconductivity.展开更多
As an important component of national talent resources, the physical conditions of college students appear to be particularly important. Based on geographic information system platform of ArcGIS, this paper builds dat...As an important component of national talent resources, the physical conditions of college students appear to be particularly important. Based on geographic information system platform of ArcGIS, this paper builds database to make a statistical analysis on the physical conditions of college students in Jiangsu province in the years of 2012 to 2016, using the analysis function and graphics. The conclusions: 1) The students’ physique conditions in Jiangsu province is in an overall downward trend;2) There are differences between the male and female college students’ physical changes;3) In view of the college students’ physical deterioration degree of agglomeration, different areas should adopt effective measures to strengthen students’ physique.展开更多
We suggest that a family of Ni-based compounds, which contain [Ni_2M_2O]~2à(M = chalcogen) layers with an antiperovskite structure constructed by mixed-anion Ni complexes, Ni M_4O_2, can be potential high tempera...We suggest that a family of Ni-based compounds, which contain [Ni_2M_2O]~2à(M = chalcogen) layers with an antiperovskite structure constructed by mixed-anion Ni complexes, Ni M_4O_2, can be potential high temperature superconductors(high-Tc) upon doping or applying pressure. The layer structures have been formed in many other transitional metal compounds such as La_2B_2Se_2O_3(B = Mn, Fe, Co). For the Ni-based compounds, we predict that the parental compounds host collinear antiferromagnetic states similar to those in iron-based high temperature superconductors. The electronic physics near Fermi energy is controlled by two egd-orbitals with completely independent in-plane kinematics. We predict that the superconductivity in this family is characterized by strong competition between extended s-wave and d-wave pairing symmetries.展开更多
We predict Co-based chalcogenides with a diamond-like structure can host unconventional high temperature superconductivity(high-Tc). The essential electronic physics in these materials stems from the Co layers with ea...We predict Co-based chalcogenides with a diamond-like structure can host unconventional high temperature superconductivity(high-Tc). The essential electronic physics in these materials stems from the Co layers with each layer being formed by vertex-shared CoA_4(A=S, Se, Te) tetrahedra complexes, a material genome proposed recently by us to host potential unconventional high-Tcclose to a d7 filling configuration in 3 d transition metal compounds. We calculate the magnetic ground states of different transition metal compounds with this structure. It is found that(Mn, Fe, Co)-based compounds all have a G-type antiferromagnetic(AFM) insulating ground state while Ni-based compounds are paramagnetic metal.The AFM interaction is the largest in the Co-based compounds as the three t2 gorbitals all strongly participate in AFM superexchange interactions. The abrupt quenching of the magnetism from the Co to Ni-based compounds is very similar to those from Fe to Co-based pnictides in which a C-type AFM state appears in the Fe-based ones but vanishes in the Co-based ones. This behavior can be considered as an electronic signature of the high-Tcgene. Upon doping, as we predicted before, this family of Co-based compounds favor a strong d-wave pairing superconducting state.展开更多
We consider possible high temperature superconductivity(high-Tc)in transition metal compounds with a cubic zinc-blende lattice structure.When the electron filling configuration in the d-shell is close to d7,all three ...We consider possible high temperature superconductivity(high-Tc)in transition metal compounds with a cubic zinc-blende lattice structure.When the electron filling configuration in the d-shell is close to d7,all three t2g orbitals are near half filling with strong nearest neighbor antiferromagnetic(AFM)superexchange interactions.We argue that upon doping,this electronic environment can be one of"genes"to host unconventional high Tcwith a time reversal symmetry broken d2x2-x2-y2±idx2-y2pairing symmetry.With gapless nodal points along the diagonal directions,this state is a direct three-dimensional analogue to the two-dimensional B1gd-wave state in cuprates.We suggest that such a case may be realized in electron doped CoN,such as CoN1-xOx and(H,Li)1-xCoN.展开更多
This study achieved the construction of earthquake disaster scenarios based on physics-based methods-from fault dynamic rupture to seismic wave propagation-and then population and economic loss estimations.The physics...This study achieved the construction of earthquake disaster scenarios based on physics-based methods-from fault dynamic rupture to seismic wave propagation-and then population and economic loss estimations.The physics-based dynamic rupture and strong ground motion simulations can fully consider the three-dimensional complexity of physical parameters such as fault geometry,stress field,rock properties,and terrain.Quantitative analysis of multiple seismic disaster scenarios along the Qujiang Fault in western Yunnan Province in southwestern China based on different nucleation locations was achieved.The results indicate that the northwestern segment of the Qujiang Fault is expected to experience significantly higher levels of damage compared to the southeastern segment.Additionally,there are significant variations in human losses,even though the economic losses are similar across different scenarios.Dali Bai Autonomous Prefecture,Chuxiong Yi Autonomous Prefecture,Yuxi City,Honghe Hani and Yi Autonomous Prefecture,and Wenshan Zhuang and Miao Autonomous Prefecture were identified as at medium to high seismic risks,with Yuxi and Honghe being particularly vulnerable.Implementing targeted earthquake prevention measures in Yuxi and Honghe will significantly mitigate the potential risks posed by the Qujiang Fault.Notably,although the fault is within Yuxi,Honghe is likely to suffer the most severe damage.These findings emphasize the importance of considering rupture directivity and its influence on ground motion distribution when assessing seismic risk.展开更多
基金the National Key R&D Program of China(Grant Nos.2018YFA0305700 and 2018YFA0305800)the National Natural Science Foundation of China(Grant Nos.12025408,11874400,11834016,11921004,11888101,and 11904391)+3 种基金the Beijing Natural Science Foundation,China(Grant No.Z190008)the Strategic Priority Research Program and Key Research Program of Frontier Sciences of Chinese Academy of Sciences(CAS)(Grant Nos.XDB25000000,XDB33000000 and QYZDBSSW-SLH013)the CAS Interdisciplinary Innovation Team(Grant No.JCTD-201-01)supported by the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Division。
文摘Recently,transition-metal-based kagome metals have aroused much research interest as a novel platform to explore exotic topological quantum phenomena.Here we report on the synthesis,structure,and physical properties of a bilayer kagome lattice compound V_(3)Sb_(2).The polycrystalline V_(3)Sb_(2) samples were synthesized by conventional solid-state-reaction method in a sealed quartz tube at temperatures below 850℃.Measurements of magnetic susceptibility and resistivity revealed consistently a density-wave-like transition at Tdw≈160 K with a large thermal hysteresis,even though some sample-dependent behaviors were observed presumably due to the different preparation conditions.Upon cooling through Tdw,no strong anomaly in lattice parameters and no indication of symmetry lowering were detected in powder x-ray diffraction measurements.This transition can be suppressed completely by applying hydrostatic pressures of about 1.8 GPa,around which no sign of superconductivity was observed down to 1.5 K.Specific-heat measurements revealed a relatively large Sommerfeld coefficientγ=18.5 mJ·mol^(-1)·K^(-2),confirming the metallic ground state with moderate electronic correlations.Density functional theory calculations indicate that V_(3)Sb_(2) shows a non-trivial topological crystalline property.Thus,our study makes V_(3)Sb_(2) a new candidate of metallic kagome compound to study the interplay between density-wave-order,nontrivial band topology,and possible superconductivity.
基金the National Key R&D Program of China(Grant No.2022YFA1403700)the National Natural Science Foundation of China(Grant Nos.12074163 and 12004030)+5 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022B1515020046,2022B1515130005,2021B1515130007,and 2020B1515120100)the Guangdong Innovative and Entrepreneurial Research Team Program(Grant Nos.2017ZT07C062 and 2019ZT08C044)the Shenzhen Science and Technology Program(Grant No.KQTD20190929173815000)Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices(Grant No.ZDSYS20190902092905285)the Shenzhen Fundamental Research Program(Grant No.JCYJ20220818100405013)China Postdoctoral Science Foundation(Grant No.2020M682780 and 2022M711495)。
文摘The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we report a titanium-based kagome metal CsTi_(3)Bi_(5)where titanium atoms form a kagome network,resembling its isostructural compound CsV_3Sb_5.Thermodynamic properties including the magnetization,resistance,and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi_(3)Bi_(5)and no signature of superconducting or charge density wave(CDW)transition anomaly down to 85 m K.Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level,consistent with the first-principles calculations.The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly.Compared to Cs V_(3)Sb_(5),the van Hove singularities are pushed far away above the Fermi level in CsTi_(3)Bi_(5),in line with the absence of CDW.Furthermore,the first-principles calculations identify the nontrivial Z_(2)topological properties for those bands crossing the Fermi level,accompanied by several local band inversions.Our results suppose CsTi_(3)Bi_(5)as a complementary platform to explore the superconductivity and nontrivial band topology.
文摘Fig.1.(a)Structure of Co_(2)N_(2) dimer.(b)Structure;of Co_(2)N_(2) layer.The dashed black lines show the mirror symmetries.X,Y coordinates are defined according to the direction of the Co Co bond,and x,y are the global coordinates in the conventional crystal structure.
文摘In our most recently published article,[1]an important reference[2]predicting CsTi_(3)Bi_(5) is missing and should be added,along with Ref.[3](originally Ref.[28]),to the introduction section.
基金supported by the National Key Basic Research Program of China(Grant No.2017YFA0303100)the National Natural Science Foundation of China(Grant Nos.11888101 and 12174428)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YBR-048)。
文摘We predict that the square lattice layer formed by[Co_(2)N_(2)]_(2)-diamond-like units can host high-temperature superconductivity.The layer appears in the stable ternary cobalt nitride,Ba Co_(2)N_(2).The electronic physics of the material stems from Co_(2)N_(2)layers where the dimerized Co pairs form a square lattice.The low energy physics near Fermi energy can be described by an effective two-orbital model.Without considering interlayer couplings,the two orbitals are effectively decoupled.This electronic structure satisfies the“gene”character proposed for unconventional high-temperature superconductors.We predict that the leading superconducting pairing instability is driven from an extended s-wave(s^(±))to a d-wave by hole doping,e.g.,in Ba_(1-x) K_(x) Co_(2)N_(2).This study provides a new platform to establish the superconducting mechanism of unconventional high-temperature superconductivity.
基金Supported by the National Key R&D Program of China(Grant No.2017YFA0303100)the National Natural Science Foundation of China(Grant No.11888101)the Strategic Priority Research Program of CAS(Grant No.XDB28000000)。
文摘We show that the layered-structure BaCuS_(2) is a moderately correlated electron system in which the electronic structure of the CuS layer bears a resemblance to those in both cuprates and iron-based superconductors.Theoretical calculations reveal that the in-plane d-p σ^(*)-bonding bands are isolated near the Fermi level.As the energy separation between the d and p orbitals are much smaller than those in cuprates and iron-based superconductors,BaCuS_(2) is expected to be moderately correlated.We suggest that this material is an ideal system to study the competitive/collaborative nature between two distinct superconducting pairing mechanisms,namely the conventional BCS electron-phonon interaction and the electron-electron correlation,which may be helpful to establish the elusive mechanism of unconventional high-temperature superconductivity.
文摘As an important component of national talent resources, the physical conditions of college students appear to be particularly important. Based on geographic information system platform of ArcGIS, this paper builds database to make a statistical analysis on the physical conditions of college students in Jiangsu province in the years of 2012 to 2016, using the analysis function and graphics. The conclusions: 1) The students’ physique conditions in Jiangsu province is in an overall downward trend;2) There are differences between the male and female college students’ physical changes;3) In view of the college students’ physical deterioration degree of agglomeration, different areas should adopt effective measures to strengthen students’ physique.
基金supported by the Ministry of Science and Technology of China(2015CB921300 and 2017YFA0303100)the National Natural Science Foundation of China(1190020,11534014,and 11334012)+1 种基金the Strategic Priority Research Program of CAS(XDB07000000)the Key Research Program of the CAS(XDPB08-1)
文摘We suggest that a family of Ni-based compounds, which contain [Ni_2M_2O]~2à(M = chalcogen) layers with an antiperovskite structure constructed by mixed-anion Ni complexes, Ni M_4O_2, can be potential high temperature superconductors(high-Tc) upon doping or applying pressure. The layer structures have been formed in many other transitional metal compounds such as La_2B_2Se_2O_3(B = Mn, Fe, Co). For the Ni-based compounds, we predict that the parental compounds host collinear antiferromagnetic states similar to those in iron-based high temperature superconductors. The electronic physics near Fermi energy is controlled by two egd-orbitals with completely independent in-plane kinematics. We predict that the superconductivity in this family is characterized by strong competition between extended s-wave and d-wave pairing symmetries.
基金supported by the Ministry of Science and Technology of China(2015CB921300 and 2017YFA0303100)the National Natural Science Foundation of China(11334012)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB07000000)
文摘We predict Co-based chalcogenides with a diamond-like structure can host unconventional high temperature superconductivity(high-Tc). The essential electronic physics in these materials stems from the Co layers with each layer being formed by vertex-shared CoA_4(A=S, Se, Te) tetrahedra complexes, a material genome proposed recently by us to host potential unconventional high-Tcclose to a d7 filling configuration in 3 d transition metal compounds. We calculate the magnetic ground states of different transition metal compounds with this structure. It is found that(Mn, Fe, Co)-based compounds all have a G-type antiferromagnetic(AFM) insulating ground state while Ni-based compounds are paramagnetic metal.The AFM interaction is the largest in the Co-based compounds as the three t2 gorbitals all strongly participate in AFM superexchange interactions. The abrupt quenching of the magnetism from the Co to Ni-based compounds is very similar to those from Fe to Co-based pnictides in which a C-type AFM state appears in the Fe-based ones but vanishes in the Co-based ones. This behavior can be considered as an electronic signature of the high-Tcgene. Upon doping, as we predicted before, this family of Co-based compounds favor a strong d-wave pairing superconducting state.
基金supported by the International Young Scientist Fellowship of Institute of Physics, Chinese Academy Sciences (Grant No. 2017002)the Strategic Priority Research Program of Chinese Academy Sciences (Grant No. XDB07000000)+3 种基金the Postdoctoral International Program from China Postdoctoral Science Foundation (Grant No. Y8BK131T61)supported by the High-performance Computing Platform of Peking Universitysupported by the National Basic Research Program of China (Grant Nos. 2015CB921300, and 2017YFA0303100)the National Natural Science Foundation of China (Grant No. NSFC-11334012)
文摘We consider possible high temperature superconductivity(high-Tc)in transition metal compounds with a cubic zinc-blende lattice structure.When the electron filling configuration in the d-shell is close to d7,all three t2g orbitals are near half filling with strong nearest neighbor antiferromagnetic(AFM)superexchange interactions.We argue that upon doping,this electronic environment can be one of"genes"to host unconventional high Tcwith a time reversal symmetry broken d2x2-x2-y2±idx2-y2pairing symmetry.With gapless nodal points along the diagonal directions,this state is a direct three-dimensional analogue to the two-dimensional B1gd-wave state in cuprates.We suggest that such a case may be realized in electron doped CoN,such as CoN1-xOx and(H,Li)1-xCoN.
基金supported by the Guangdong Provincial Key Laboratory of Geophysical High-Resolution Imaging Technology (2022B1212010002)Key Special Project for Introduced Talents Team of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0203)the Shenzhen Science and Technology Program (KQTD20170810111725321)
文摘This study achieved the construction of earthquake disaster scenarios based on physics-based methods-from fault dynamic rupture to seismic wave propagation-and then population and economic loss estimations.The physics-based dynamic rupture and strong ground motion simulations can fully consider the three-dimensional complexity of physical parameters such as fault geometry,stress field,rock properties,and terrain.Quantitative analysis of multiple seismic disaster scenarios along the Qujiang Fault in western Yunnan Province in southwestern China based on different nucleation locations was achieved.The results indicate that the northwestern segment of the Qujiang Fault is expected to experience significantly higher levels of damage compared to the southeastern segment.Additionally,there are significant variations in human losses,even though the economic losses are similar across different scenarios.Dali Bai Autonomous Prefecture,Chuxiong Yi Autonomous Prefecture,Yuxi City,Honghe Hani and Yi Autonomous Prefecture,and Wenshan Zhuang and Miao Autonomous Prefecture were identified as at medium to high seismic risks,with Yuxi and Honghe being particularly vulnerable.Implementing targeted earthquake prevention measures in Yuxi and Honghe will significantly mitigate the potential risks posed by the Qujiang Fault.Notably,although the fault is within Yuxi,Honghe is likely to suffer the most severe damage.These findings emphasize the importance of considering rupture directivity and its influence on ground motion distribution when assessing seismic risk.
