The van der Waals(vdW)MnSb4Te7is a newly synthesized antiferromagnetic(AFM)topological insulator hosting a robust axion insulator state irrelative to the specific spin structure.However,the intrinsic hole doped charac...The van der Waals(vdW)MnSb4Te7is a newly synthesized antiferromagnetic(AFM)topological insulator hosting a robust axion insulator state irrelative to the specific spin structure.However,the intrinsic hole doped character of MnSb_4Te_7makes the Fermi level far away from the Dirac point of about 180 meV,which is unfavorable for the exploration of exotic topological properties such as the quantum anomalous Hall effect(QAHE).To shift up the Fermi level close to the Dirac point,the strategy of partially replacing Sb with Bi as Mn(Sb_(1-x)Bi_(x))_(4)Te_(7)was tried and the magnetotransport properties,in particular,the anomalous Hall effect,were measured and analyzed.Through the electron doping,the anomalous Hall conductanceσAH changes from negative to positive between x=0.3 and 0.5,indicative of a possible topological transition.Besides,a charge neutrality point(CNP)also appears between x=0.6 and 0.7.The results would be instructive for further understanding the interplay between nontrivial topological states and the magnetism,as well as for the exploration of exotic topological properties.展开更多
In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it ...In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it is predicted that in the nonrelativistic limit of certain collinear antiferromagnets, there exists a type of chiral“Dirac-like” fermion, whose dispersion manifests four-fold degenerate crossing points formed by spin-degenerate linear bands, with topologically protected Fermi arcs. Such an unconventional chiral fermion, protected by a hidden SU(2) symmetry in the hierarchy of an enhanced crystallographic group, namely spin space group, is not experimentally verified yet. Here, by angle-resolved photoemission spectroscopy measurements, we reveal the surface origin of the electron pocket at the Fermi surface in collinear antiferromagnet CoNb3S6. Combining with neutron diffraction and first-principles calculations, we suggest a multidomain collinear antiferromagnetic configuration, rendering the the existence of the Fermi-arc surface states induced by chiral Dirac-like fermions.Our work provides spectral evidence of the chiral Dirac-like fermion caused by particular spin symmetry in CoNb_(3)S_(6), paving an avenue for exploring new emergent phenomena in antiferromagnets with unconventional quasiparticle excitations.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
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.
Unconventional fermions in the immensely studied topological semimetals are the source for rich exotic topological properties.Here,using symmetry analysis and first-principles calculations,we propose the coexistence o...Unconventional fermions in the immensely studied topological semimetals are the source for rich exotic topological properties.Here,using symmetry analysis and first-principles calculations,we propose the coexistence of multiple topological nodal structure in LaSb_(2),including topological nodal surfaces,nodal lines and in particular eightfold degenerate nodal points,which have been scarcely observed in a single material.Further,utilizing angle-resolved photoemission spectroscopy,we confirm the existence of nodal surfaces and eightfold degenerate nodal points in LaSb_(2).The intriguing multiple topological nodal structure might play a crucial role in giving rise to the large linear magnetoresistance.Our work renews the insights into the exotic topological phenomena in LaSb_(2).展开更多
Polyimides are widely used in the MEMS and flexible electronics fields due to their combined physicochemical properties,including high thermal stability,mechanical strength,and chemical resistance values.In the past d...Polyimides are widely used in the MEMS and flexible electronics fields due to their combined physicochemical properties,including high thermal stability,mechanical strength,and chemical resistance values.In the past decade,rapid progress has been made in the microfabrication of polyimides.However,enabling technologies,such as laser-induced graphene on polyimide,photosensitive polyimide micropatterning,and 3D polyimide microstructure assembly,have not been reviewed from the perspective of polyimide microfabrication.The aims of this review are to systematically discuss polyimide microfabrication techniques,which cover flm formation,material conversion,micropatterning,3D microfabrication,and their applications.With an emphasis on polyimide-based flexible MEMS devices,we discuss the remaining technological challenges in polyimide fabrication and possible technological innovations in this field.展开更多
Using angle-resolved photoemission spectroscopy(ARPES) and low-energy electron diffraction(LEED), together with densityfunctional theory(DFT) calculation, we report the formation of charge density wave(CDW) and its in...Using angle-resolved photoemission spectroscopy(ARPES) and low-energy electron diffraction(LEED), together with densityfunctional theory(DFT) calculation, we report the formation of charge density wave(CDW) and its interplay with the Kondo effect and topological states in CeSbTe. The observed Fermi surface(FS) exhibits parallel segments that can be well connected by the observed CDWordering vector, indicating that the CDWorder is driven by the electron-phonon coupling(EPC) as a result of the nested FS. The CDW gap is large(~0.3 eV) and momentum-dependent, which naturally explains the robust CDWorder up to high temperatures. The gap opening leads to a reduced density of states(DOS) near the Fermi level(EF), which correspondingly suppresses the many-body Kondo effect, leading to very localized 4 f electrons at 20 K and above. The topological Dirac cone at the X point is found to remain gapless inside the CDW phase. Our results provide evidence for the competition between CDWand the Kondo effect in a Kondo lattice system. The robust CDWorder in CeSbTe and related compounds provide an opportunity to search for the long-sought-after axionic insulator.展开更多
This paper presents a novel flexible airflow sensor based on four curved microcantilevers arranged in a cross-form configuration.A self-bending method based on MEMS technology has been used to fabricate the curved mic...This paper presents a novel flexible airflow sensor based on four curved microcantilevers arranged in a cross-form configuration.A self-bending method based on MEMS technology has been used to fabricate the curved microcantilevers structure,and this method can transfer a 2D plane structure into a 3D structure with good consistency in the morphology.The curved microcantilever consists of a polyimide(PI)top layer,silicon(Si)bottom layer,and platinum(Pt)piezoresistor at the root of the cantilever.The difference in the in-plane residual stress between the PI and Si layers bent the microcantilever upward.The curved-up microcantilever transfers the fluidic momentum that acts on it to drag force,which deflects the curved-up microcantilever and changes the resistance of the piezoresistor.To realize temperature compensation and decrease the noise,a reference resistor and an ambient temperature detector were integrated for the Wheatstone half-bridge measurement and temperature monitoring,respectively.The cross-form configuration of the curved-up cantilevers has high sensitivity advantages and possesses direction-sensing ability.Experimental results show that the sensitivity of the sensors increased as a function of the airflow velocity,and the sensors exhibited a maximum resolution of 4 mm⋅s^(−1) and a maximum sensitivity of 60.35 mV⋅(ms^(−1))^(−1) when the airflow velocity was larger than 38.5 m⋅s^(−1).展开更多
LaIrIn5 is a reference compound of the heavy-fermion superconductor LaIrIn5.The lack of f electrons in LaIrIn5 indicates that there should not be any f electron participating in the construction of its Fermi surface.T...LaIrIn5 is a reference compound of the heavy-fermion superconductor LaIrIn5.The lack of f electrons in LaIrIn5 indicates that there should not be any f electron participating in the construction of its Fermi surface.Thus the electronic structure comparison between LaIrIn5 and LaIrIn5 provides a good platform to study the properties of f electrons.Here angle-resolved photoemission spectroscopy(ARPES)measurements and density functional theory(DFT)calculations are performed to study the electronic structures of LaIrIn5 and LaIrIn5.We find the valence band structures of the two materials are similar to each other,except for the absence of f bands in LaIrIn5.By analyzing the Fermi crossings of the three conduction bands of the two materials quantitatively,we find the volumes of the electron pocketsαandβaround the M′point become larger from LaIrIn5 to LaIrIn5,while the hole pocketγaround theΓ′point becomes smaller.Together with the calculation results,we confirm that this is mainly originated from the f-electron contribution,while the lattice-constant difference between LaIrIn5 and LaIrIn5 only has a finite influence.We also give a summary of the f-electron character in its related Ce-115 heavy fermion compounds.Our results may be essential for the complete microscopic understanding of the 115 compounds and the related heavy-fermion systems.展开更多
Biological flow receptors show astonishing performance and are used as models for the design of novel flow sensors.However,the functional importance of interfacial microstructures is seldom discussed in previous revie...Biological flow receptors show astonishing performance and are used as models for the design of novel flow sensors.However,the functional importance of interfacial microstructures is seldom discussed in previous review papers.Herein,this review summarises the underlying biomechanical principles in the biological flow receptors and describes the recent progress in bio-inspired flow sensors,in which the underlying sensing-enhancement mechanisms are emphasised.展开更多
基金the Shanghai Science and Technology Innovation Action Plan(Grant No.21JC1402000)the National Natural Science Foundation of China(Grant No.12004405)+3 种基金the State Key Laboratory of Functional Materials for Informatics(Grant No.SKL2022)the Double FirstClass Initiative Fund of ShanghaiTech University,the Analytical Instrumentation Center(Grant No.SPST-AIC10112914)SPST,and ShanghaiTech Universitythe State Key Laboratory of Surface Physics and Department of Physics of Fudan University(Grant No.KF2022_13)。
文摘The van der Waals(vdW)MnSb4Te7is a newly synthesized antiferromagnetic(AFM)topological insulator hosting a robust axion insulator state irrelative to the specific spin structure.However,the intrinsic hole doped character of MnSb_4Te_7makes the Fermi level far away from the Dirac point of about 180 meV,which is unfavorable for the exploration of exotic topological properties such as the quantum anomalous Hall effect(QAHE).To shift up the Fermi level close to the Dirac point,the strategy of partially replacing Sb with Bi as Mn(Sb_(1-x)Bi_(x))_(4)Te_(7)was tried and the magnetotransport properties,in particular,the anomalous Hall effect,were measured and analyzed.Through the electron doping,the anomalous Hall conductanceσAH changes from negative to positive between x=0.3 and 0.5,indicative of a possible topological transition.Besides,a charge neutrality point(CNP)also appears between x=0.6 and 0.7.The results would be instructive for further understanding the interplay between nontrivial topological states and the magnetism,as well as for the exploration of exotic topological properties.
基金supported by the National Key R&D Program of China (Grant Nos. 2020YFA0308900 and 2022YFA1403700)the National Natural Science Foundation of China (Grant Nos. 12074163, 12134020, 11974157, 12104255, 12004159, and 12374146)+8 种基金Guangdong Provincial Key Laboratory for Computational Science and Material Design (Grant No. 2019B030301001)the Science, Technology and Innovation Commission of Shenzhen Municipality (Grant Nos. ZDSYS20190902092905285 and KQTD20190929173815000)Guangdong Basic and Applied Basic Research Foundation (Grant Nos. 2022B1515020046, 2021B1515130007, 2022A1515011915, 2019A1515110712, and 2022B1515130005)Shenzhen Science and Technology Program (Grant Nos. RCJC20221008092722009 and RCBS20210706092218039)the Guangdong Innovative and Entrepreneurial Research Team Program (Grant No. 2019ZT08C044)the beam time awarded by Australia’s Nuclear Science and Technology Organisation (ANSTO) (Grant No. P8130)the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex (J-PARC) was performed under a user program (Proposal No. 2019B0140)performed at the Hiroshima Synchrotron Radiation Center (HiSOR) of Japan (Grant Nos. 22BG023 and 22BG029)Shanghai Synchrotron Radiation Facility (SSRF) BL03U (Grant No. 2022-SSRF-PT-020848)。
文摘In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it is predicted that in the nonrelativistic limit of certain collinear antiferromagnets, there exists a type of chiral“Dirac-like” fermion, whose dispersion manifests four-fold degenerate crossing points formed by spin-degenerate linear bands, with topologically protected Fermi arcs. Such an unconventional chiral fermion, protected by a hidden SU(2) symmetry in the hierarchy of an enhanced crystallographic group, namely spin space group, is not experimentally verified yet. Here, by angle-resolved photoemission spectroscopy measurements, we reveal the surface origin of the electron pocket at the Fermi surface in collinear antiferromagnet CoNb3S6. Combining with neutron diffraction and first-principles calculations, we suggest a multidomain collinear antiferromagnetic configuration, rendering the the existence of the Fermi-arc surface states induced by chiral Dirac-like fermions.Our work provides spectral evidence of the chiral Dirac-like fermion caused by particular spin symmetry in CoNb_(3)S_(6), paving an avenue for exploring new emergent phenomena in antiferromagnets with unconventional quasiparticle excitations.
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 R&D Program of China(Grant No.2023YFA1406304)the National Natural Science Foundation of China(Grant Nos.U2032208,12222413,11874264,12074181,11834006,and 12104217)+9 种基金the Natural Science Foundation of Shanghai(Grant Nos.23ZR1482200,22ZR1473300,and 14ZR1447600)the Shanghai Science and Technology Innovation Action Plan(Grant No.21JC1402000)the Open Projects from State Key Laboratory of Functional Materials for Informatics(Grant No.SKL2022)the Double First-Class Initiative Fund of Shanghai Tech Universitythe fund of Science and Technology on Surface Physics and Chemistry Laboratory(Grant No.6142A02200102)supported by ME2Project(Grant No.11227902)from the National Natural Science Foundation of Chinasupported by the National Key Projects for Research and Development of China(Grant No.2021YFA1400400)the Fundamental Research Funds for the Central Universities(Grant No.020414380185)the Natural Science Foundation of Jiangsu Province(Grant No.BK20200007)the Fok Ying-Tong Education Foundation of China(Grant No.161006)。
文摘Unconventional fermions in the immensely studied topological semimetals are the source for rich exotic topological properties.Here,using symmetry analysis and first-principles calculations,we propose the coexistence of multiple topological nodal structure in LaSb_(2),including topological nodal surfaces,nodal lines and in particular eightfold degenerate nodal points,which have been scarcely observed in a single material.Further,utilizing angle-resolved photoemission spectroscopy,we confirm the existence of nodal surfaces and eightfold degenerate nodal points in LaSb_(2).The intriguing multiple topological nodal structure might play a crucial role in giving rise to the large linear magnetoresistance.Our work renews the insights into the exotic topological phenomena in LaSb_(2).
基金supported by the National Natural Science Foundation of China(T2121003,No.52022008,51975030)partially supported by the Bejing Municipal Natural Science Foundation(M22021).
文摘Polyimides are widely used in the MEMS and flexible electronics fields due to their combined physicochemical properties,including high thermal stability,mechanical strength,and chemical resistance values.In the past decade,rapid progress has been made in the microfabrication of polyimides.However,enabling technologies,such as laser-induced graphene on polyimide,photosensitive polyimide micropatterning,and 3D polyimide microstructure assembly,have not been reviewed from the perspective of polyimide microfabrication.The aims of this review are to systematically discuss polyimide microfabrication techniques,which cover flm formation,material conversion,micropatterning,3D microfabrication,and their applications.With an emphasis on polyimide-based flexible MEMS devices,we discuss the remaining technological challenges in polyimide fabrication and possible technological innovations in this field.
基金supported by the National Key R&D Program of the Ministry of Science and Technology of China (Grant Nos. 2016YFA0300203, and 2017YFA0303100)the National Science Foundation of China (Grant Nos. 11674280, and 11774305)+1 种基金the Science Challenge Program of ChinaPart of this research used Beam line 03U of the Shanghai Synchrotron Radiation Facility, which was supported by ME2 Project (Grant No. 11227902) from the National Natural Science Foundation of China。
文摘Using angle-resolved photoemission spectroscopy(ARPES) and low-energy electron diffraction(LEED), together with densityfunctional theory(DFT) calculation, we report the formation of charge density wave(CDW) and its interplay with the Kondo effect and topological states in CeSbTe. The observed Fermi surface(FS) exhibits parallel segments that can be well connected by the observed CDWordering vector, indicating that the CDWorder is driven by the electron-phonon coupling(EPC) as a result of the nested FS. The CDW gap is large(~0.3 eV) and momentum-dependent, which naturally explains the robust CDWorder up to high temperatures. The gap opening leads to a reduced density of states(DOS) near the Fermi level(EF), which correspondingly suppresses the many-body Kondo effect, leading to very localized 4 f electrons at 20 K and above. The topological Dirac cone at the X point is found to remain gapless inside the CDW phase. Our results provide evidence for the competition between CDWand the Kondo effect in a Kondo lattice system. The robust CDWorder in CeSbTe and related compounds provide an opportunity to search for the long-sought-after axionic insulator.
基金supported financially by the National Natural Science Foundation of China under contract No.51975030 and No.52022008.
文摘This paper presents a novel flexible airflow sensor based on four curved microcantilevers arranged in a cross-form configuration.A self-bending method based on MEMS technology has been used to fabricate the curved microcantilevers structure,and this method can transfer a 2D plane structure into a 3D structure with good consistency in the morphology.The curved microcantilever consists of a polyimide(PI)top layer,silicon(Si)bottom layer,and platinum(Pt)piezoresistor at the root of the cantilever.The difference in the in-plane residual stress between the PI and Si layers bent the microcantilever upward.The curved-up microcantilever transfers the fluidic momentum that acts on it to drag force,which deflects the curved-up microcantilever and changes the resistance of the piezoresistor.To realize temperature compensation and decrease the noise,a reference resistor and an ambient temperature detector were integrated for the Wheatstone half-bridge measurement and temperature monitoring,respectively.The cross-form configuration of the curved-up cantilevers has high sensitivity advantages and possesses direction-sensing ability.Experimental results show that the sensitivity of the sensors increased as a function of the airflow velocity,and the sensors exhibited a maximum resolution of 4 mm⋅s^(−1) and a maximum sensitivity of 60.35 mV⋅(ms^(−1))^(−1) when the airflow velocity was larger than 38.5 m⋅s^(−1).
基金supported by the National Natural Science Foundation of China(Grant Nos.11874330,11774320,U1630248,and 11904334)the National Key Research and Development Program of China(Grant No.2017YFA0303104)+5 种基金the National Key R&D Program of the MOST of China(Grant No.2016YFA0300204)the special fund from Institute of Materials,CAEP(Grant No.TP02201904)the Equipment development fund(Grant No.JZX7Y201901SY00900107)the Science Challenge Project(Grant No.TZ2016004)Part of this research used Beamline 03U of the Shanghai Synchron Radiation Facility,which is supported by ME2 project under contract No.11227902 from National Natural Science Foundation of Chinasupported by“Award for Outstanding Member in Youth Innovation Promotion Association CAS”。
文摘LaIrIn5 is a reference compound of the heavy-fermion superconductor LaIrIn5.The lack of f electrons in LaIrIn5 indicates that there should not be any f electron participating in the construction of its Fermi surface.Thus the electronic structure comparison between LaIrIn5 and LaIrIn5 provides a good platform to study the properties of f electrons.Here angle-resolved photoemission spectroscopy(ARPES)measurements and density functional theory(DFT)calculations are performed to study the electronic structures of LaIrIn5 and LaIrIn5.We find the valence band structures of the two materials are similar to each other,except for the absence of f bands in LaIrIn5.By analyzing the Fermi crossings of the three conduction bands of the two materials quantitatively,we find the volumes of the electron pocketsαandβaround the M′point become larger from LaIrIn5 to LaIrIn5,while the hole pocketγaround theΓ′point becomes smaller.Together with the calculation results,we confirm that this is mainly originated from the f-electron contribution,while the lattice-constant difference between LaIrIn5 and LaIrIn5 only has a finite influence.We also give a summary of the f-electron character in its related Ce-115 heavy fermion compounds.Our results may be essential for the complete microscopic understanding of the 115 compounds and the related heavy-fermion systems.
基金supported by the National Natural Science Foundation of China(grant no.51575027 and 51975030).
文摘Biological flow receptors show astonishing performance and are used as models for the design of novel flow sensors.However,the functional importance of interfacial microstructures is seldom discussed in previous review papers.Herein,this review summarises the underlying biomechanical principles in the biological flow receptors and describes the recent progress in bio-inspired flow sensors,in which the underlying sensing-enhancement mechanisms are emphasised.