Hybrid structures of two distinct materials provide an excellent opportunity to optimize functionalities.We report the realization of wide quantum Hall plateaus in graphene field-effect devices on the LaAlO3/SrTiO3 he...Hybrid structures of two distinct materials provide an excellent opportunity to optimize functionalities.We report the realization of wide quantum Hall plateaus in graphene field-effect devices on the LaAlO3/SrTiO3 heterostructures.Well-defined quantized Hall resistance plateaus at filling factors ν=±2 can be obtained over wide ranges of the magnetic field and gate voltage,e.g.,extending from 2 T to a maximum available magnetic field of 9 T.By using a simple band diagram model,it is revealed that these wide plateaus arise from the ultralarge capacitance of the ultra-thin LAO layer acting as the dielectric layer.This is distinctly different from the case of epitaxial graphene on Si C substrates,where the realization of giant Hall plateaus relies on the charge transfer between the graphene layer and interface states in SiC.Our results offer an alternative route towards optimizing the quantum Hall performance of graphene,which may find its applications in the further development of quantum resistance metrology.展开更多
Self-assembled monolayers(SAMs)have been commonly employed as hole-selective layers(HSLs)in inverted(p-i-n)perovskite solar cells(PSCs),and typically only a single-component SAM is applied,which plays limited role in ...Self-assembled monolayers(SAMs)have been commonly employed as hole-selective layers(HSLs)in inverted(p-i-n)perovskite solar cells(PSCs),and typically only a single-component SAM is applied,which plays limited role in selective hole transport.Herein,we synthesize a novel SAM,(4-(3,11-dibro mo-7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid(Br-4PADBC),and apply it as a complementary component to the commonly used[2-(3,6-dimeth oxy-9H-carbazol-9-yl)ethyl]phosphonic acid(MeO-2PACz)SAM,accomplishing boosted hole transport in inverted PSCs.A series of characterizations and theoretical calculations are employed to unravel the roles of each components within the binary SAM(bi-SAM).The involvements of the non-planar dibenzo[c,g]carbazole unit and electron-withdrawing Br atoms induce larger dipole moment of Br-4PADBC than MeO-2PACz,resulting in much deeper work function of ITO and consequently improved alignment with the valence band energy level of perovskite.Besides,the introduced Br atoms improve the quality of perovskite crystals and help passivate defects of perovskite.On the other hand,the existence of the conventional MeO-2PACz SAM ensures the considerable conductivity of the bi-SAM and thus efficient hole extraction from the perovskite layer.As a result,inverted PSC devices based on bi-SAM HSL deliver a decent power conversion efficiency(PCE)of 24.52%as well as dramatically improved thermal and operational stabilities.展开更多
Superconductivity at the 2D limit shows emergent novel quantum phenomena, including anomalously enhanced H_(c2),quantum metallic states and quantum Griffiths singularity, which has attracted much attention in the fiel...Superconductivity at the 2D limit shows emergent novel quantum phenomena, including anomalously enhanced H_(c2),quantum metallic states and quantum Griffiths singularity, which has attracted much attention in the field of condensed matter physics. In this article, we focus on new advances in quasi-2D superconductors in the bulk phase using an organic molecular electrochemical intercalation method. The enhanced superconductivity and emergent pseudogap behavior in these quasi-2D superconductors are summarized with a further prospect.展开更多
Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic properties.Typically,the underlying electronic structure would determinate the physical properti...Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic properties.Typically,the underlying electronic structure would determinate the physical properties of materials.But as for now,limited studies have been done to reveal the underlying electronic structure of this material system,comparing to the huge amount of investigations on the material synthesis.The effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic phenomena.In pristine CsPbBr_(3),the Fr?hlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass renormalization.In this regard,it would be very interesting to explore the electronic structure in doped LHPs.Here,we report high-resolution angle-resolved photoemission spectroscopy(ARPES) studies on both pristine and Cl-doped CsPbBr_(3).The experimental band dispersions are extracted from ARPES spectra along both ■ and ■ high symmetry directions.DFT calculations are performed and directly compared with the ARPES data.Our results have revealed the band structure of Cl-doped CsPbBr_(3) for the first time,which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr_(3) compound.Doping dependent measurements indicate that the chlorine doping could moderately tune the renormalization strength.These results will help understand the physical properties of LHPs as a function of doping.展开更多
Ruddlesden-Popper iridate Sr_(3)Ir_(2)O_(7)is a spin-orbit coupled Mott insulator.Hole doped Sr_(3)Ir_(2)O_(7)provides an ideal platform to study the exotic quantum phenomena that occur near the metal-insulator transi...Ruddlesden-Popper iridate Sr_(3)Ir_(2)O_(7)is a spin-orbit coupled Mott insulator.Hole doped Sr_(3)Ir_(2)O_(7)provides an ideal platform to study the exotic quantum phenomena that occur near the metal-insulator transition(MIT)region.Rh substitution of Ir is an effective method to induce hole doping into Sr_(3)Ir_(2)O_(7).However,the highest doping level reported in Sr_(3)(Ir_(1-x)Rh_(x))_(2)O_(7)single crystals was only around 3%,which is far from the MIT region.In this paper,we report the successful growth of single crystals of Sr3(Ir_(1-x)Rh_(x))_(2)O_(7)with a doping level of~9%.The samples have been fully characterized,demonstrating the high quality of the single crystals.Transport measurements have been carried out,confirming the tendency of MIT in these samples.The electronic structure has also been examined by angle-resolved photoemission spectroscopy(ARPES)measurements.Our results establish a platform to investigate the heavily hole doped Sr_(3)Ir_(2)O_(7) compound,which also provide new insights into the MIT with hole doping in this material system.展开更多
We carried out experimental investigations of the geometric effect on the electronic behavior in Pb_(1-x)Bi_(x) thin films by scanning tunneling microscopy and spectroscopy.Single crystal monolayer Pb_(0.74)Bi_(0.26) ...We carried out experimental investigations of the geometric effect on the electronic behavior in Pb_(1-x)Bi_(x) thin films by scanning tunneling microscopy and spectroscopy.Single crystal monolayer Pb_(0.74)Bi_(0.26) and two-monolayer Pb_(0.75)Bi_(0.25)Pb_(1-x)Bi_(x) thin films were fabricated by molecular beam epitaxy,where large surface corrugations were observed.Combined with tunneling spectroscopic measurements,it is found that atomic corrugations can widely change the electronic behaviors.These findings show that the Pb_(1-x)Bi_(x) system can be a promising platform to further explore geometry-decorated electronic behavior in two-dimensional metallic thin films.展开更多
Controlling the anomalous Hall effect(AHE)inspires potential applications of quantum materials in the next generation of electronics.The recently discovered quasi-2D kagome superconductor CsV_(3)Sb_(5) exhibits large ...Controlling the anomalous Hall effect(AHE)inspires potential applications of quantum materials in the next generation of electronics.The recently discovered quasi-2D kagome superconductor CsV_(3)Sb_(5) exhibits large AHE accompanying with the charge-density-wave(CDW)order which provides us an ideal platform to study the interplay among nontrivial band topology,CDW,and unconventional superconductivity.Here,we systematically investigated the pressure effect of the AHE in CsV_(3)Sb_(5).Our high-pressure transport measurements confirm the concurrence of AHE and CDW in the compressed CsV_(3)Sb_(5).Remarkably,distinct from the negative AHE at ambient pressure,a positive anomalous Hall resistivity sets in below 35 K with pressure around 0.75 GPa,which can be attributed to the Fermi surface reconstruction and/or Fermi energy shift in the new CDW phase under pressure.Our work indicates that the anomalous Hall effect in CsV_(3)Sb_(5) is tunable and highly related to the band structure.展开更多
The driving mechanism of nematicity and its twist with superconductivity in iron-based superconductors are still under debate.Recently,a dominant B1g-type strain effect on superconductivity is observed in underdoped i...The driving mechanism of nematicity and its twist with superconductivity in iron-based superconductors are still under debate.Recently,a dominant B1g-type strain effect on superconductivity is observed in underdoped iron-pnictides superconductors Ba(Fe_(1-x)Co_(x))_(2)As_(2),suggesting a strong interplay between nematicity and superconductivity.Since the long-range spin order is absent in FeSe superconductor,whether a similar strain effect could be also observed or not is an interesting question.Here,by utilizing a flexible film as substrate,we successfully achieve a wide-range-strain tuning of FeSe thin flake,in which both the tensile and compressive strain could reach up to~0.7%,and systematically study the strain effect on both superconducting and nematic transition(T_(c)and Ts)in the FeSe thin flake.Our results reveal a predominant A1g-type strain effect on T_(c).Meanwhile,Ts exhibits a monotonic anti-correlation with T_(c)and the maximum T_(c)reaches to 12 K when Ts is strongly suppressed under the maximum compressive strain.Finally,in comparison with the results in the underdoped Ba(Fe_(1-x)Co_(x))_(2)As_(2),the absence of B1g-type strain effect in FeSe further supports the role of stripe-type spin fluctuations on superconductivity.In addition,our work also supports that the orbital degree of freedom plays a key role to drive the nematic transition in FeSe.展开更多
The two-dimensional(2 D)kagome superconductor Cs V_(3)Sb_(5) has attracted much recent attention due to the coexistence of superconductivity,charge orders,topology and kagome physics,which manifest themselves as disti...The two-dimensional(2 D)kagome superconductor Cs V_(3)Sb_(5) has attracted much recent attention due to the coexistence of superconductivity,charge orders,topology and kagome physics,which manifest themselves as distinct electronic structures in both bulk and surface states of the material.An interesting next step is to manipulate the electronic states in this system.Here,we report angle-resolved photoemission spectroscopy(ARPES)evidence for a surface-induced orbitalselective band reconstruction in Cs V_(3)Sb_(5).A significant energy shift of the electron-like band aroundΓand a moderate energy shift of the hole-like band around M are observed as a function of time.This evolution is reproduced in a much shorter time scale by in-situ annealing of the Cs V_(3)Sb_(5) sample.Orbital-resolved density functional theory(DFT)calculations reveal that the momentum-dependent band reconstruction is associated with different orbitals for the bands aroundΓand M,and the time-dependent evolution points to the change of sample surface that is likely caused by the formation of Cs vacancies on the surface.Our results indicate the possibility of orbital-selective control of the band structure via surface modification,which may open a new avenue for manipulating exotic phenomena in this material system,including superconductivity.展开更多
Recently discovered kagome metals AV_(3)Sb_(5)(A=K,Rb,and Cs)provide an ideal platform to study the correlation among nontrivial band topology,unconventional charge density wave(CDW),and superconductivity.The evolutio...Recently discovered kagome metals AV_(3)Sb_(5)(A=K,Rb,and Cs)provide an ideal platform to study the correlation among nontrivial band topology,unconventional charge density wave(CDW),and superconductivity.The evolution of electronic structures associated with the change of lattice modulations is crucial for understanding of the CDW mechanism,with the combination of angle-resolved photoemission spectroscopy(ARPES)measurements and density functional theory calculations,we investigate how band dispersions change with the increase of lattice distortions.In particular,we focus on the electronic states around M point,where the van Hove singularities are expected to play crucial roles in the CDW transition.Previous ARPES studies reported a spectral weight splitting of the van Hove singularity around M point,which is associated with the 3D lattice modulations.Our studies reveal that this“splitting”can be connected to the two van Hove singularities at k_(z)=0 and k_(z)=π/c in the normal states.When the electronic system enters into the CDW state,both van Hove singularities move down.Such novel properties are important for understanding of the CDW transition.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos.11974324,11804326 and U1832151)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No.XDC07010000)+2 种基金the National Key Research and Development Program of China (Grant No.2017YFA0403600)Anhui Initiative in Quantum Information Technologies (Grant No.AHY170000)Hefei Science Center CAS (Grant No.2018HSC-UE014)。
文摘Hybrid structures of two distinct materials provide an excellent opportunity to optimize functionalities.We report the realization of wide quantum Hall plateaus in graphene field-effect devices on the LaAlO3/SrTiO3 heterostructures.Well-defined quantized Hall resistance plateaus at filling factors ν=±2 can be obtained over wide ranges of the magnetic field and gate voltage,e.g.,extending from 2 T to a maximum available magnetic field of 9 T.By using a simple band diagram model,it is revealed that these wide plateaus arise from the ultralarge capacitance of the ultra-thin LAO layer acting as the dielectric layer.This is distinctly different from the case of epitaxial graphene on Si C substrates,where the realization of giant Hall plateaus relies on the charge transfer between the graphene layer and interface states in SiC.Our results offer an alternative route towards optimizing the quantum Hall performance of graphene,which may find its applications in the further development of quantum resistance metrology.
基金the National Natural Science Foundation of China(51925206,U1932214,52302052)the National Natural Science Foundation of China(52322318)+6 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0450301)the Fundamental Research Funds for the Central Universities(WK2060000051,20720220009)the National Key Research and Development Program of China(No.2023YFB3809700)the Innovation and Technology Fund(GHP/100/20SZ,GHP/102/20GD,MRP/040/21X,ITS/147/22FP)the Research Grants Council of Hong Kong Grant(N_City U102/23,C4005-22Y,C1055-23G,11306521)the Green Tech Fund(GTF202020164)the Science Technology and Innovation Committee of Shenzhen Municipality(SGDX20210823104002015,JCYJ20220818101018038)。
文摘Self-assembled monolayers(SAMs)have been commonly employed as hole-selective layers(HSLs)in inverted(p-i-n)perovskite solar cells(PSCs),and typically only a single-component SAM is applied,which plays limited role in selective hole transport.Herein,we synthesize a novel SAM,(4-(3,11-dibro mo-7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid(Br-4PADBC),and apply it as a complementary component to the commonly used[2-(3,6-dimeth oxy-9H-carbazol-9-yl)ethyl]phosphonic acid(MeO-2PACz)SAM,accomplishing boosted hole transport in inverted PSCs.A series of characterizations and theoretical calculations are employed to unravel the roles of each components within the binary SAM(bi-SAM).The involvements of the non-planar dibenzo[c,g]carbazole unit and electron-withdrawing Br atoms induce larger dipole moment of Br-4PADBC than MeO-2PACz,resulting in much deeper work function of ITO and consequently improved alignment with the valence band energy level of perovskite.Besides,the introduced Br atoms improve the quality of perovskite crystals and help passivate defects of perovskite.On the other hand,the existence of the conventional MeO-2PACz SAM ensures the considerable conductivity of the bi-SAM and thus efficient hole extraction from the perovskite layer.As a result,inverted PSC devices based on bi-SAM HSL deliver a decent power conversion efficiency(PCE)of 24.52%as well as dramatically improved thermal and operational stabilities.
基金Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB25000000)the National Natural Science Foundation of China (Grant No. 11888101)+2 种基金the National Key R&D Program of China (Grant No. 2017YFA0303001)the Anhui Initiative in Quantum Information Technologies, China (Grant No. AHY160000)the Key Research Program of Frontier Sciences, CAS (Grant No. QYZDYSSW-SLH021)。
文摘Superconductivity at the 2D limit shows emergent novel quantum phenomena, including anomalously enhanced H_(c2),quantum metallic states and quantum Griffiths singularity, which has attracted much attention in the field of condensed matter physics. In this article, we focus on new advances in quasi-2D superconductors in the bulk phase using an organic molecular electrochemical intercalation method. The enhanced superconductivity and emergent pseudogap behavior in these quasi-2D superconductors are summarized with a further prospect.
基金Project supported by the International Partnership Program of the Chinese Academy of Sciences(Grant No.123GJHZ2022035MI)the Fundamental Research Funds for the Central Universities(Grant Nos.WK3510000015 and WK3510000012)。
文摘Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic properties.Typically,the underlying electronic structure would determinate the physical properties of materials.But as for now,limited studies have been done to reveal the underlying electronic structure of this material system,comparing to the huge amount of investigations on the material synthesis.The effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic phenomena.In pristine CsPbBr_(3),the Fr?hlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass renormalization.In this regard,it would be very interesting to explore the electronic structure in doped LHPs.Here,we report high-resolution angle-resolved photoemission spectroscopy(ARPES) studies on both pristine and Cl-doped CsPbBr_(3).The experimental band dispersions are extracted from ARPES spectra along both ■ and ■ high symmetry directions.DFT calculations are performed and directly compared with the ARPES data.Our results have revealed the band structure of Cl-doped CsPbBr_(3) for the first time,which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr_(3) compound.Doping dependent measurements indicate that the chlorine doping could moderately tune the renormalization strength.These results will help understand the physical properties of LHPs as a function of doping.
基金supported by the USTC start-up fundthe National Natural Science Foundation of China(Grant Nos.12074358 and 12004363)+2 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.WK3510000008 and WK2030000035)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302802)supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences under Contract No.DEAC02-76SF00515。
文摘Ruddlesden-Popper iridate Sr_(3)Ir_(2)O_(7)is a spin-orbit coupled Mott insulator.Hole doped Sr_(3)Ir_(2)O_(7)provides an ideal platform to study the exotic quantum phenomena that occur near the metal-insulator transition(MIT)region.Rh substitution of Ir is an effective method to induce hole doping into Sr_(3)Ir_(2)O_(7).However,the highest doping level reported in Sr_(3)(Ir_(1-x)Rh_(x))_(2)O_(7)single crystals was only around 3%,which is far from the MIT region.In this paper,we report the successful growth of single crystals of Sr3(Ir_(1-x)Rh_(x))_(2)O_(7)with a doping level of~9%.The samples have been fully characterized,demonstrating the high quality of the single crystals.Transport measurements have been carried out,confirming the tendency of MIT in these samples.The electronic structure has also been examined by angle-resolved photoemission spectroscopy(ARPES)measurements.Our results establish a platform to investigate the heavily hole doped Sr_(3)Ir_(2)O_(7) compound,which also provide new insights into the MIT with hole doping in this material system.
基金Project supported by the National Key Basic Research Program of China(Grant No.2017YFA0205004)the National Natural Science Foundation of China(Grant Nos.92165201,11474261,and 11634011)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.WK3510000006)the Anhui Initiative Fund in Quantum Information Technologies(Grant No.AHY170000)。
文摘We carried out experimental investigations of the geometric effect on the electronic behavior in Pb_(1-x)Bi_(x) thin films by scanning tunneling microscopy and spectroscopy.Single crystal monolayer Pb_(0.74)Bi_(0.26) and two-monolayer Pb_(0.75)Bi_(0.25)Pb_(1-x)Bi_(x) thin films were fabricated by molecular beam epitaxy,where large surface corrugations were observed.Combined with tunneling spectroscopic measurements,it is found that atomic corrugations can widely change the electronic behaviors.These findings show that the Pb_(1-x)Bi_(x) system can be a promising platform to further explore geometry-decorated electronic behavior in two-dimensional metallic thin films.
基金the National Key Research and Development Program of China(Grant Nos.2019YFA0704900 and 2017YFA0303001)the Anhui Initiative in Quantum Information Technologies(Grant No.AHY160000)+5 种基金the Science Challenge Project of China(Grant No.TZ2016004)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS)(Grant No.QYZDYSSWSLH021)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB25000000)the National Natural Science Foundation of China(Grants Nos.11888101 and 11534010)the Collaborative Innovation Program of Hefei Science Center,CAS(Grant No.2020HSC-CIP014)the Fundamental Research Funds for the Central Universities,China(Grant No.WK3510000011).
文摘Controlling the anomalous Hall effect(AHE)inspires potential applications of quantum materials in the next generation of electronics.The recently discovered quasi-2D kagome superconductor CsV_(3)Sb_(5) exhibits large AHE accompanying with the charge-density-wave(CDW)order which provides us an ideal platform to study the interplay among nontrivial band topology,CDW,and unconventional superconductivity.Here,we systematically investigated the pressure effect of the AHE in CsV_(3)Sb_(5).Our high-pressure transport measurements confirm the concurrence of AHE and CDW in the compressed CsV_(3)Sb_(5).Remarkably,distinct from the negative AHE at ambient pressure,a positive anomalous Hall resistivity sets in below 35 K with pressure around 0.75 GPa,which can be attributed to the Fermi surface reconstruction and/or Fermi energy shift in the new CDW phase under pressure.Our work indicates that the anomalous Hall effect in CsV_(3)Sb_(5) is tunable and highly related to the band structure.
基金Project supported by the National Key R&D Program of China(Grant Nos.2017YFA0303000 and 2016YFA0300201)the National Natural Science Foundation of China(Grant No.11888101)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB25000000)the Anhui Initiative in Quantum Information Technologies(Grant No.AHY160000).
文摘The driving mechanism of nematicity and its twist with superconductivity in iron-based superconductors are still under debate.Recently,a dominant B1g-type strain effect on superconductivity is observed in underdoped iron-pnictides superconductors Ba(Fe_(1-x)Co_(x))_(2)As_(2),suggesting a strong interplay between nematicity and superconductivity.Since the long-range spin order is absent in FeSe superconductor,whether a similar strain effect could be also observed or not is an interesting question.Here,by utilizing a flexible film as substrate,we successfully achieve a wide-range-strain tuning of FeSe thin flake,in which both the tensile and compressive strain could reach up to~0.7%,and systematically study the strain effect on both superconducting and nematic transition(T_(c)and Ts)in the FeSe thin flake.Our results reveal a predominant A1g-type strain effect on T_(c).Meanwhile,Ts exhibits a monotonic anti-correlation with T_(c)and the maximum T_(c)reaches to 12 K when Ts is strongly suppressed under the maximum compressive strain.Finally,in comparison with the results in the underdoped Ba(Fe_(1-x)Co_(x))_(2)As_(2),the absence of B1g-type strain effect in FeSe further supports the role of stripe-type spin fluctuations on superconductivity.In addition,our work also supports that the orbital degree of freedom plays a key role to drive the nematic transition in FeSe.
基金supported by the Fundamental Research Funds for the Central Universities(Grant Nos.WK3510000008 and WK3510000012)USTC start-up fund+3 种基金supported by the UC Santa Barbara NSF Quantum Foundry funded via the Q-AMASE-i program under award DMR-1906325the NSF Materials Research Science and Engineering Center at UC Santa Barbara(DMR-1720256)support from the California Nano Systems Institute through the Elings Fellowship programsupported by the National Science Foundation Graduate Research Fellowship Program under Grant No.DGE1650114。
文摘The two-dimensional(2 D)kagome superconductor Cs V_(3)Sb_(5) has attracted much recent attention due to the coexistence of superconductivity,charge orders,topology and kagome physics,which manifest themselves as distinct electronic structures in both bulk and surface states of the material.An interesting next step is to manipulate the electronic states in this system.Here,we report angle-resolved photoemission spectroscopy(ARPES)evidence for a surface-induced orbitalselective band reconstruction in Cs V_(3)Sb_(5).A significant energy shift of the electron-like band aroundΓand a moderate energy shift of the hole-like band around M are observed as a function of time.This evolution is reproduced in a much shorter time scale by in-situ annealing of the Cs V_(3)Sb_(5) sample.Orbital-resolved density functional theory(DFT)calculations reveal that the momentum-dependent band reconstruction is associated with different orbitals for the bands aroundΓand M,and the time-dependent evolution points to the change of sample surface that is likely caused by the formation of Cs vacancies on the surface.Our results indicate the possibility of orbital-selective control of the band structure via surface modification,which may open a new avenue for manipulating exotic phenomena in this material system,including superconductivity.
基金supported by the National Key R&D Program of China (Grant No.2017YFA0402901)the National Natural Science Foundation of China (Grant No.U2032153)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDB25000000)the Users with Excellence Program of Hefei Science Center of the Chinese Academy of Sciences (Grant No.2021HSC-UE004)。
文摘Recently discovered kagome metals AV_(3)Sb_(5)(A=K,Rb,and Cs)provide an ideal platform to study the correlation among nontrivial band topology,unconventional charge density wave(CDW),and superconductivity.The evolution of electronic structures associated with the change of lattice modulations is crucial for understanding of the CDW mechanism,with the combination of angle-resolved photoemission spectroscopy(ARPES)measurements and density functional theory calculations,we investigate how band dispersions change with the increase of lattice distortions.In particular,we focus on the electronic states around M point,where the van Hove singularities are expected to play crucial roles in the CDW transition.Previous ARPES studies reported a spectral weight splitting of the van Hove singularity around M point,which is associated with the 3D lattice modulations.Our studies reveal that this“splitting”can be connected to the two van Hove singularities at k_(z)=0 and k_(z)=π/c in the normal states.When the electronic system enters into the CDW state,both van Hove singularities move down.Such novel properties are important for understanding of the CDW transition.
