We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe.Based on first-principles density functional theory calculations,we study the electronic str...We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe.Based on first-principles density functional theory calculations,we study the electronic structures,Fermi-surface quantum fluctuations,as well as phonon properties of the antiferromagnetic kagome metal FeGe.It is found that charge density wave emerges in such a system due to a subtle cooperation between electron-electron interactions and electron–phonon couplings,which gives rise to an unusual scenario of interaction-triggered phonon instabilities,and eventually yields a charge density wave(CDW)state.We further show that,in the CDW phase,the ground-state current density distribution exhibits an intriguing star-of-David pattern,leading to flux density modulation.The orbital fluxes(or current loops)in this system emerge as a result of the subtle interplay between magnetism,lattice geometries,charge order,and spin-orbit coupling(SOC),which can be described by a simple,yet universal,tight-binding theory including a Kane-Mele-type SOC term and a magnetic exchange interaction.We further study the origin of the peculiar step-edge states in FeGe,which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.展开更多
Here we review scanning tunneling microscopy research on the surface determination for various types of kagome materials,including 11-type(CoSn,FeSn,FeGe),32-type(Fe_(3)Sn_(2)),13-type(Mn_(3)Sn),135-type(AV_(3)Sb_(5),...Here we review scanning tunneling microscopy research on the surface determination for various types of kagome materials,including 11-type(CoSn,FeSn,FeGe),32-type(Fe_(3)Sn_(2)),13-type(Mn_(3)Sn),135-type(AV_(3)Sb_(5),A=K,Rb,Cs),166-type(TbMn6Sn_(6),YMn_(6)Sn_(6)and ScV_(6)Sn_(6)),and 322-type(Co_(3)Sn_(2)S_(2)and Ni_(3)In_(2)Se_(2)).We first demonstrate that the measured step height between different surfaces typically deviates from the expected value of±0.4∼0.8Å,which is owing to the tunneling convolution effect with electronic states and becomes a serious issue for Co_(3)Sn_(2)S_(2)where the expected Sn-S interlayer distance is 0.6Å.Hence,we put forward a general methodology for surface determination as atomic step geometry imaging,which is fundamental but also experimentally challenging to locate the step and to image with atomic precision.We discuss how this method can be used to resolve the surface termination puzzle in Co_(3)Sn_(2)S_(2).This method provides a natural explanation for the existence of adatoms and vacancies,and beyond using unknown impurity states,we propose and use designer layer-selective substitutional chemical markers to confirm the validity of this method.Finally,we apply this method to determine the surface of a new kagome material Ni_(3)In_(2)Se_(2),as a cousin of Co_(3)Sn_(2)S_(2),and we image the underlying kagome geometry on the determined Se surface above the kagome layer,which directly visualizes the p-d hybridization physics.We emphasize that this general method does not rely on theory,but the determined surface identity can provide guidelines for first-principles calculations with adjustable parameters on the surface-dependent local density of states and quasi-particle interference patterns.展开更多
Exchange bias(EB)in ferromagnetic/antiferromagnetic materials is a novel idea for high-density spintronic devices.Van der Waals(vdW)heterostructures offer a promising solution,enabling a“Lego”like assembly without i...Exchange bias(EB)in ferromagnetic/antiferromagnetic materials is a novel idea for high-density spintronic devices.Van der Waals(vdW)heterostructures offer a promising solution,enabling a“Lego”like assembly without interface or adding dopants,opposite to traditional heterostructures.However,in typical vdW heterostructures,the EB effect exists at low temperatures and only one polarity.This work addresses these challenges by using Fe_(3)GaTe_(2)/NiPS_(3) heterostructures whose EB can survive at higher temperatures and polarities flip.The exchange bias(EB)of the device persists up to 150 K and can have its polarity reversed by altering the stacking direction during fabrication.Simultaneously,an anomalous Hall effect(A_(HE))with a coercive field of approximately 0.9 T is observed at 5 K and remains detectable up to 300 K.The device further shows the spin-orbit torque(SOT)-induced magnetization switching up to room temperature.Under low field-cooling conditions(e.g.,≥2 mT),we observe an EB field(HEB)up to 1 mT,which reached 110 mT at 1.5 T.HEB becomes zero above 150 K,showing a non-discernible EB effect,whereas the A_(HE) persists up to room temperature.Similarly,in the Fe_(3)GaTe_(2)/NiPS_(3) and NiPS_(3)/Fe_(3)GaTe_(2),different stacking layers at the interface induce the net magnetic effect and flip the magnetization direction due to magnetic domains at the Fe_(3)GaTe_(2) layer.The results show that strong interlayer coupling within these layers generates significant A_(HE) and high HEB with blocking temperatures up to 150 K,making it suitable for the new 2D spintronic device applications.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12174257)the National Key R&D program of China(Grant No.2020YFA0309601)+1 种基金the Science and Technology Commission of the Shanghai Municipality(Grant No.21JC1405100)the Start-Up Grant of ShanghaiTech University。
文摘We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe.Based on first-principles density functional theory calculations,we study the electronic structures,Fermi-surface quantum fluctuations,as well as phonon properties of the antiferromagnetic kagome metal FeGe.It is found that charge density wave emerges in such a system due to a subtle cooperation between electron-electron interactions and electron–phonon couplings,which gives rise to an unusual scenario of interaction-triggered phonon instabilities,and eventually yields a charge density wave(CDW)state.We further show that,in the CDW phase,the ground-state current density distribution exhibits an intriguing star-of-David pattern,leading to flux density modulation.The orbital fluxes(or current loops)in this system emerge as a result of the subtle interplay between magnetism,lattice geometries,charge order,and spin-orbit coupling(SOC),which can be described by a simple,yet universal,tight-binding theory including a Kane-Mele-type SOC term and a magnetic exchange interaction.We further study the origin of the peculiar step-edge states in FeGe,which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.
基金supported by the National Natural Science Foundation of China(11734003,62275016,12274029,and 92163206)the National Key Research and Development Program of China(2020YFA0308800)+1 种基金Beijing Natural Science Foundation(Z210006 and Z190006)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB30000000)。
基金support from the National Key R&D Program of China(No.2023YFA1407300)the National Science Foundation of China(No.12374060)+1 种基金Project funded by China Postdoctoral Science Foundation(No.2023M741546,No.2023M731530)The work at Princeton is supported by Gordon and Betty Moore Foundation(GBMF4547 and GBMF9461,M.Z.H.).
文摘Here we review scanning tunneling microscopy research on the surface determination for various types of kagome materials,including 11-type(CoSn,FeSn,FeGe),32-type(Fe_(3)Sn_(2)),13-type(Mn_(3)Sn),135-type(AV_(3)Sb_(5),A=K,Rb,Cs),166-type(TbMn6Sn_(6),YMn_(6)Sn_(6)and ScV_(6)Sn_(6)),and 322-type(Co_(3)Sn_(2)S_(2)and Ni_(3)In_(2)Se_(2)).We first demonstrate that the measured step height between different surfaces typically deviates from the expected value of±0.4∼0.8Å,which is owing to the tunneling convolution effect with electronic states and becomes a serious issue for Co_(3)Sn_(2)S_(2)where the expected Sn-S interlayer distance is 0.6Å.Hence,we put forward a general methodology for surface determination as atomic step geometry imaging,which is fundamental but also experimentally challenging to locate the step and to image with atomic precision.We discuss how this method can be used to resolve the surface termination puzzle in Co_(3)Sn_(2)S_(2).This method provides a natural explanation for the existence of adatoms and vacancies,and beyond using unknown impurity states,we propose and use designer layer-selective substitutional chemical markers to confirm the validity of this method.Finally,we apply this method to determine the surface of a new kagome material Ni_(3)In_(2)Se_(2),as a cousin of Co_(3)Sn_(2)S_(2),and we image the underlying kagome geometry on the determined Se surface above the kagome layer,which directly visualizes the p-d hybridization physics.We emphasize that this general method does not rely on theory,but the determined surface identity can provide guidelines for first-principles calculations with adjustable parameters on the surface-dependent local density of states and quasi-particle interference patterns.
基金National Natural Science Foundation of China,Grant/Award Numbers:5221101553,T2394475Key R&D Projects in Anhui Province,Grant/Award Number:2022i01020012+8 种基金Natural Science Foundation of Hefei,Grant/Award Number:2022039Excellent Research and Innovation Team Project of Anhui Province,Grant/Award Number:2022AH010001Beijing Natural Science Foundation,Grant/Award Number:4232070International Mobility Project,Grant/Award Number:B16001Gordon and Betty Moore Foundation,Grant/Award Number:GBMF9461US DOE,Grant/Award Number:DOE/BES DE-FG-02-05ER46200Deanship of Research and Graduate Studies at King Khalid University,Grant/Award Number:RGP-2/712/46National Science and Technology Major Project,Grant/Award Number:2025ZD0613804Hefei Zhongke Kele New Materials Co.Ltd.,Grant/Award Number:2024340104003776。
文摘Exchange bias(EB)in ferromagnetic/antiferromagnetic materials is a novel idea for high-density spintronic devices.Van der Waals(vdW)heterostructures offer a promising solution,enabling a“Lego”like assembly without interface or adding dopants,opposite to traditional heterostructures.However,in typical vdW heterostructures,the EB effect exists at low temperatures and only one polarity.This work addresses these challenges by using Fe_(3)GaTe_(2)/NiPS_(3) heterostructures whose EB can survive at higher temperatures and polarities flip.The exchange bias(EB)of the device persists up to 150 K and can have its polarity reversed by altering the stacking direction during fabrication.Simultaneously,an anomalous Hall effect(A_(HE))with a coercive field of approximately 0.9 T is observed at 5 K and remains detectable up to 300 K.The device further shows the spin-orbit torque(SOT)-induced magnetization switching up to room temperature.Under low field-cooling conditions(e.g.,≥2 mT),we observe an EB field(HEB)up to 1 mT,which reached 110 mT at 1.5 T.HEB becomes zero above 150 K,showing a non-discernible EB effect,whereas the A_(HE) persists up to room temperature.Similarly,in the Fe_(3)GaTe_(2)/NiPS_(3) and NiPS_(3)/Fe_(3)GaTe_(2),different stacking layers at the interface induce the net magnetic effect and flip the magnetization direction due to magnetic domains at the Fe_(3)GaTe_(2) layer.The results show that strong interlayer coupling within these layers generates significant A_(HE) and high HEB with blocking temperatures up to 150 K,making it suitable for the new 2D spintronic device applications.
