Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and ...Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and unstable,making high-quality single-crystal growth,characterization,and measurements difficult,and most do not exhibit superconductivity at ambient pressure.In contrast,La_(3) In stands out for its ambient-pressure superconductivity(T_(C)∼9.4 K)and the availability of high-quality single crystals.Here,we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations.The bands near the Fermi energy(E_(F))are mainly derived from La 5d and In 5p orbitals.A saddle point is directly observed at the Brillouin zone(BZ)boundary,while a three-dimensional Van Hove singularity crosses E_(F) at the BZ corner.First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_(F).The coexistence of a high density of states and in-gap topological surface states near𝐸F suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.展开更多
The spatially-resolved laser-based high-resolution angle resolved photoemission spectroscopy(ARPES) measurements have been performed on the optimally-doped YBa_(2)Cu_(3)O_(7)-σ(Y123) superconductor. For the first tim...The spatially-resolved laser-based high-resolution angle resolved photoemission spectroscopy(ARPES) measurements have been performed on the optimally-doped YBa_(2)Cu_(3)O_(7)-σ(Y123) superconductor. For the first time, we found the region from the cleaved surface that reveals clear bulk electronic properties. The intrinsic Fermi surface and band structures of Y123 were observed. The Fermi surface-dependent and momentum-dependent superconducting gap was determined which is nodeless and consistent with the d+is gap form.展开更多
Altermagnets represent a newly discovered class of magnetically ordered materials.Among all the candidates,CrSb stands out due to its largest spin splitting energy and highest Néel temperature exceeding 700 K,mak...Altermagnets represent a newly discovered class of magnetically ordered materials.Among all the candidates,CrSb stands out due to its largest spin splitting energy and highest Néel temperature exceeding 700 K,making it promising for room-temperature spintronic applications.Here we have successfully grown high quality CrSb(100)thin film on GaAs(110)substrate by molecular beam epitaxy.Using angle-resolved photoemission spectroscopy,we successfully obtained the three-dimensional electronic structure of the thin film.Moreover,we observed the emergence of the altermagnetic splitting bands corresponding to the calculated results along the low symmetry pathsT-QandP-D.The bands near the Fermi level are only spin splitting bands along theP-Ddirection,with splitting energy reaching as high as 910 meV.This finding provides insights into the magnetic properties of CrSb thin films and paves the way for further studies on their electronic structure and potential applications in spintronics.展开更多
LiV_(2)O_(4)is a spinel-structured compound that stands out as the first known 3d-electron system exhibiting typical heavy fermion behavior.A central question is how such strong mass renormalization emerges in the abs...LiV_(2)O_(4)is a spinel-structured compound that stands out as the first known 3d-electron system exhibiting typical heavy fermion behavior.A central question is how such strong mass renormalization emerges in the absence of f-electrons.In this work,we investigate the three-dimensional electronic structure of LiV_(2)O_(4)thin films using angle-resolved photoemission spectroscopy.We identify that an electron-like flat band is derived from a_(1g)orbitals,along with a highly dispersive e′_(g)band strongly coupled with phonons.The overall agreement with dynamical mean-field theory calculations highlights the essential role of inter-orbital Hund’s coupling in reducing the a_(1g)bandwidth to 25 meV,approaching a Mott state.Notably,we find that heavy-fermion behavior arises from additional renormalization at the a_(1g)band near the Fermi level,likely driven by many-body interactions at energy scales down to a few meV and potentially linked to geometric frustration inherent to the spinel lattice.These results provide crucial insights into the origin of the heavy fermion behavior in 3d-electron systems.展开更多
The layered van der Waals(vdW)ferroelectric CuInP_(2)S_(6) (CIPS)exhibits unique cation-hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promise for advanced appl...The layered van der Waals(vdW)ferroelectric CuInP_(2)S_(6) (CIPS)exhibits unique cation-hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promise for advanced applications in nanoelectronics.However,an explicit analysis of its lattice dynamics and vibrational symmetries,pivotal for understanding the material’s peculiar ferroelectric and ferroionic behaviors,remains incomplete.Here,we employ angle-resolved polarized Raman spectroscopy in concert with first-principles calculations to systematically unravel the anisotropic lattice vibrations of CIPS single crystals.By analyzing the polarization-dependent Raman intensities,we determine the symmetry assignments and Raman tensors of all major vibrational modes,revealing good agreement with theoretical predictions.Furthermore,we demonstrate the utility of Raman spectroscopy as a sensitive and non-invasive probe for structural and ferroelectric order evolution by examining temperature-driven phase transitions and thickness-dependent polarization suppression in CIPS.Our findings establish a foundational framework for correlating lattice dynamics with functional properties in CIPS and provide a methodological blueprint for studying other vdW ferroelectrics.展开更多
The sub-atomic precision of molecular beam epitaxy(MBE)allows for highly flexible elemental doping in nanowires(NWs).Optimizing doping quality for specific elements requires a comprehensive understanding of the relati...The sub-atomic precision of molecular beam epitaxy(MBE)allows for highly flexible elemental doping in nanowires(NWs).Optimizing doping quality for specific elements requires a comprehensive understanding of the relationship between process parameters and doping concentrations.This necessitates in-situ monitoring of the doping process to define the corresponding process window.However,the reflection high-energy electron diffraction(RHEED)technique,commonly used during MBE growth,has limited sensitivity to atomic arrangement changes caused by doping and is primarily capable of monitoring the structural quality of the sample.To address this limitation,we propose a nanowire doping concentration measurement method based on angle-resolved scatterometry(ARS).This method captures scattering information across the full angular range of NWs,allowing for high-resolution measurement of doping concentration.Using GaN NWs and AlN films doped with Si as a case study,we measured the Si concentration at different doping temperatures.The results demonstrate that the proposed method achieves a doping concentration resolution of 0.01%and 0.06%within the investigated temperature range.Furthermore,we employed deep learning to establish the relationship between angle-resolved reflectivity and nominal doping concentration.The predictive results indicate that the measurement error is maintained below 0.027%.We also validated the robustness of the method across multiple measurement wavelengths and explored the feasibility of using reduced angle reflectance for neural network training.This work paves the way for in-situ monitoring of nanowire doping processes through ARS,significantly enhancing doping control precision in MBE growth.展开更多
Atomic intercalation in two-dimensional （2D） layered materials can be used to engineer the electronic structure at the atomic scale and generate tuneable physical and chemical properties which are quite distinct in ...Atomic intercalation in two-dimensional （2D） layered materials can be used to engineer the electronic structure at the atomic scale and generate tuneable physical and chemical properties which are quite distinct in comparison with the pristine material. Among them, electron-doped engineering induced by intercalation is an efficient route to modulate electronic states in 2D layers. Herein, we demonstrate a semiconducting to metallic phase transition in zirconium diselenide （ZrSe2） single crystals via controllable incorporation of copper （Cu） atoms. Our angle resolved photoemission spectroscopy （ARPES） measurements and first-principles density functional theory （DFT） calculations dearly revealed the emergence of conduction band dispersion at the M/L point of the Brillouin zone due to Cu-induced electron doping in ZrSe2 interlayers. Moreover, electrical measurements in ZrSe2 revealed semiconducting behavior, while the Cu-intercalated ZrSe2 exhibited a linear current-voltage curve with metallic character. The atomic intercalation approach may have high potential for realizing transparent electron-doping systems for many specific 2D-based nanoelectronic applications.展开更多
The intercalation of metal is a promising method for the modulating electronic properties in transition metal dichalcogenides(TMDs).However,there still lacks enough knowledge about how the intercalated atoms directly ...The intercalation of metal is a promising method for the modulating electronic properties in transition metal dichalcogenides(TMDs).However,there still lacks enough knowledge about how the intercalated atoms directly impact the two-dimensional structural layers and modulate the band structures therein.Taking advantage of X-ray absorption fine structure and angle-resolved photoemission spectroscopy,we studied how Cu intercalation influences the host TaSe2 layers in Cu0.03TaSe2 crystals.The intercalated Cu atoms form bonds with Se of the host layers,and there is charge transfer from Cu to Se.By examining the changes of band dispersions,we show that the variation of electronic structures is beyond a simple rigid band model with merely charge doping effect.This work'reveals that the unusual change of band dispersions is associated with the formation of bonds between the intercalated metal elements and anion ions in the host layers,and provides a reference for the comprehensive understanding of the electronic structures in intercalated materials.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12222413,12174443,12274459,and 12404266)the National Key R&D Program of China(Grant Nos.2023YFA1406500,2022YFA1403800,and 2022YFA1403103)+3 种基金the Natural Science Foundation of Shanghai (Grant No.23ZR1482200)the Natural Science Foundation of Ningbo (Grant No.2024J019)the Science Research Project of Hebei Education Department (Grant No.BJ2025060)the funding of Ningbo Yongjiang Talent Program。
文摘Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and unstable,making high-quality single-crystal growth,characterization,and measurements difficult,and most do not exhibit superconductivity at ambient pressure.In contrast,La_(3) In stands out for its ambient-pressure superconductivity(T_(C)∼9.4 K)and the availability of high-quality single crystals.Here,we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations.The bands near the Fermi energy(E_(F))are mainly derived from La 5d and In 5p orbitals.A saddle point is directly observed at the Brillouin zone(BZ)boundary,while a three-dimensional Van Hove singularity crosses E_(F) at the BZ corner.First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_(F).The coexistence of a high density of states and in-gap topological surface states near𝐸F suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11888101 and 11974404)the National Key Research and Development Program of China (Grant Nos. 2021YFA1401800 and 2018YFA0704200)+3 种基金the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant Nos. XDB25000000 and XDB33000000)the Youth Innovation Promotion Association of CAS (Grant No. Y2021006)Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0301800)the Synergetic Extreme Condition User Facility (SECUF)。
文摘The spatially-resolved laser-based high-resolution angle resolved photoemission spectroscopy(ARPES) measurements have been performed on the optimally-doped YBa_(2)Cu_(3)O_(7)-σ(Y123) superconductor. For the first time, we found the region from the cleaved surface that reveals clear bulk electronic properties. The intrinsic Fermi surface and band structures of Y123 were observed. The Fermi surface-dependent and momentum-dependent superconducting gap was determined which is nodeless and consistent with the d+is gap form.
基金supported by the National Key R&D Program of China[Grant No.2023YFA1406304(J J)]the National Natural Science Foundation of China[Grant No.12174362(J J)]+2 种基金the Innovation Program for Quantum Science and Technology[Grant No.2021ZD0302803(D L F)]the New Cornerstone Science Foundation(D L F)Beamline 03U of the Shanghai Synchrotron Radiation Facility,which is supported by ME2 project under contract No.11227902 from the National Natural Science Foundation of China。
文摘Altermagnets represent a newly discovered class of magnetically ordered materials.Among all the candidates,CrSb stands out due to its largest spin splitting energy and highest Néel temperature exceeding 700 K,making it promising for room-temperature spintronic applications.Here we have successfully grown high quality CrSb(100)thin film on GaAs(110)substrate by molecular beam epitaxy.Using angle-resolved photoemission spectroscopy,we successfully obtained the three-dimensional electronic structure of the thin film.Moreover,we observed the emergence of the altermagnetic splitting bands corresponding to the calculated results along the low symmetry pathsT-QandP-D.The bands near the Fermi level are only spin splitting bands along theP-Ddirection,with splitting energy reaching as high as 910 meV.This finding provides insights into the magnetic properties of CrSb thin films and paves the way for further studies on their electronic structure and potential applications in spintronics.
基金support of Dr.Z.T.Liu,Dr.Z.C.Jiang,Dr.Marta Zonno,and Dr.Sergey Gorovikovsupported in part by the National Key R&D Program of the MOST of China(Grant No.2023YFA1406300)+4 种基金the National Natural Science Foundation of China(Grant Nos.12274085,12422404,and 92477206)the New Cornerstone Science Foundation,the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302803)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)The ARPES measurements used Beamlines 09U and 03U of the SSRF and Beamline QMSC of Canadian Light sourcesupported by the ME2 project from the National Natural Science Foundation of China(Contract No.11227902).
文摘LiV_(2)O_(4)is a spinel-structured compound that stands out as the first known 3d-electron system exhibiting typical heavy fermion behavior.A central question is how such strong mass renormalization emerges in the absence of f-electrons.In this work,we investigate the three-dimensional electronic structure of LiV_(2)O_(4)thin films using angle-resolved photoemission spectroscopy.We identify that an electron-like flat band is derived from a_(1g)orbitals,along with a highly dispersive e′_(g)band strongly coupled with phonons.The overall agreement with dynamical mean-field theory calculations highlights the essential role of inter-orbital Hund’s coupling in reducing the a_(1g)bandwidth to 25 meV,approaching a Mott state.Notably,we find that heavy-fermion behavior arises from additional renormalization at the a_(1g)band near the Fermi level,likely driven by many-body interactions at energy scales down to a few meV and potentially linked to geometric frustration inherent to the spinel lattice.These results provide crucial insights into the origin of the heavy fermion behavior in 3d-electron systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.12474089,12574102 for L.Y.and L.F.,and 12404102 for J.Z.)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions(for L.Y.and L.F.)+2 种基金the Natural Science Foundation of the Jiangsu Province(Grant No.BK20230806 for J.Z.)Southeast University Interdisciplinary Research Program for Young Scholars(Grant No.2024FGC1008 for J.Z.)the support by the State Key Laboratory of Solid State Microstructures(Nanjing University)(No.M37067)。
文摘The layered van der Waals(vdW)ferroelectric CuInP_(2)S_(6) (CIPS)exhibits unique cation-hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promise for advanced applications in nanoelectronics.However,an explicit analysis of its lattice dynamics and vibrational symmetries,pivotal for understanding the material’s peculiar ferroelectric and ferroionic behaviors,remains incomplete.Here,we employ angle-resolved polarized Raman spectroscopy in concert with first-principles calculations to systematically unravel the anisotropic lattice vibrations of CIPS single crystals.By analyzing the polarization-dependent Raman intensities,we determine the symmetry assignments and Raman tensors of all major vibrational modes,revealing good agreement with theoretical predictions.Furthermore,we demonstrate the utility of Raman spectroscopy as a sensitive and non-invasive probe for structural and ferroelectric order evolution by examining temperature-driven phase transitions and thickness-dependent polarization suppression in CIPS.Our findings establish a foundational framework for correlating lattice dynamics with functional properties in CIPS and provide a methodological blueprint for studying other vdW ferroelectrics.
基金supported by the National Natural Science Foundation of China under Grant No.62204173Hainan Province Science and Technology Special Fund under Grant ZDYF2023GXJS005+7 种基金Collaborative Innovation Center of Information Technology,Hainan University(XTCX2022XXB03)Hubei Key Laboratory of Electronic Manufacturing and Packaging Integration(Wuhan University)(Grant No.EMPI2024022)Major Program(JD)of Hubei Province(No.2023BAA008)Jiangsu Province Engineering Research Center of Integrated Circuit Advanced Assembly and Test,China(No.NTIKFJJ202305)the Open Fund Project of the State Key Laboratory of Intelligent Vehicle Safety Technology(IVSTSKL-202308)Hainan University Research Initiation Fund Project(XJ2400011663)The National Key R&D Program of China(2024YFC2816900)The Science and Technology special fund of Hainan Province NO.ZDYF2024GXJS303.
文摘The sub-atomic precision of molecular beam epitaxy(MBE)allows for highly flexible elemental doping in nanowires(NWs).Optimizing doping quality for specific elements requires a comprehensive understanding of the relationship between process parameters and doping concentrations.This necessitates in-situ monitoring of the doping process to define the corresponding process window.However,the reflection high-energy electron diffraction(RHEED)technique,commonly used during MBE growth,has limited sensitivity to atomic arrangement changes caused by doping and is primarily capable of monitoring the structural quality of the sample.To address this limitation,we propose a nanowire doping concentration measurement method based on angle-resolved scatterometry(ARS).This method captures scattering information across the full angular range of NWs,allowing for high-resolution measurement of doping concentration.Using GaN NWs and AlN films doped with Si as a case study,we measured the Si concentration at different doping temperatures.The results demonstrate that the proposed method achieves a doping concentration resolution of 0.01%and 0.06%within the investigated temperature range.Furthermore,we employed deep learning to establish the relationship between angle-resolved reflectivity and nominal doping concentration.The predictive results indicate that the measurement error is maintained below 0.027%.We also validated the robustness of the method across multiple measurement wavelengths and explored the feasibility of using reduced angle reflectance for neural network training.This work paves the way for in-situ monitoring of nanowire doping processes through ARS,significantly enhancing doping control precision in MBE growth.
文摘Atomic intercalation in two-dimensional （2D） layered materials can be used to engineer the electronic structure at the atomic scale and generate tuneable physical and chemical properties which are quite distinct in comparison with the pristine material. Among them, electron-doped engineering induced by intercalation is an efficient route to modulate electronic states in 2D layers. Herein, we demonstrate a semiconducting to metallic phase transition in zirconium diselenide （ZrSe2） single crystals via controllable incorporation of copper （Cu） atoms. Our angle resolved photoemission spectroscopy （ARPES） measurements and first-principles density functional theory （DFT） calculations dearly revealed the emergence of conduction band dispersion at the M/L point of the Brillouin zone due to Cu-induced electron doping in ZrSe2 interlayers. Moreover, electrical measurements in ZrSe2 revealed semiconducting behavior, while the Cu-intercalated ZrSe2 exhibited a linear current-voltage curve with metallic character. The atomic intercalation approach may have high potential for realizing transparent electron-doping systems for many specific 2D-based nanoelectronic applications.
基金We acknowledge the financial support from the National Key R&D Program of China(No.2017YFA0402901,2016YFA0401004)National Natural Science Foundation of China(No.11674296,21727801 and 11621063)+1 种基金the Key Research Program of the Chinese Academy of Sciences(No.XDPB01)the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology(No.2018CXFX002),NSFC-MAECI(51861135202).
文摘The intercalation of metal is a promising method for the modulating electronic properties in transition metal dichalcogenides(TMDs).However,there still lacks enough knowledge about how the intercalated atoms directly impact the two-dimensional structural layers and modulate the band structures therein.Taking advantage of X-ray absorption fine structure and angle-resolved photoemission spectroscopy,we studied how Cu intercalation influences the host TaSe2 layers in Cu0.03TaSe2 crystals.The intercalated Cu atoms form bonds with Se of the host layers,and there is charge transfer from Cu to Se.By examining the changes of band dispersions,we show that the variation of electronic structures is beyond a simple rigid band model with merely charge doping effect.This work'reveals that the unusual change of band dispersions is associated with the formation of bonds between the intercalated metal elements and anion ions in the host layers,and provides a reference for the comprehensive understanding of the electronic structures in intercalated materials.
