The kagome superconductor CsV_(3)Sb_(5) has attracted widespread attention due to its rich correlated electron states including superconductivity, charge density wave(CDW), nematicity, and pair density wave. Notably, ...The kagome superconductor CsV_(3)Sb_(5) has attracted widespread attention due to its rich correlated electron states including superconductivity, charge density wave(CDW), nematicity, and pair density wave. Notably, the modulation of the intertwined electronic orders by the chemical doping is significant to illuminate the cooperation/competition between multiple phases in kagome superconductors. In this study, we have synthesized a series of tantalum-substituted Cs(V_(1-x)Ta_(x))_(3)Sb_(5) by a modified self-flux method. Electrical transport measurements reveal that CDW is suppressed gradually and becomes undetectable as the doping content of x is over 0.07. Concurrently, the superconductivity is enhanced monotonically from T_(c) ~ 2.8 K at x = 0 to 5.2 K at x = 0.12. Intriguingly, in the absence of CDW, Cs(V_(1-x)Ta_(x))_(3)Sb_(5)(x = 0.12) crystals exhibit a pronounced two-fold symmetry of the in-plane angular-dependent magnetoresistance(AMR) in the superconducting state, indicating the anisotropic superconducting properties in the Cs(V_(1-x)Ta_(x))_(3)Sb_(5). Our findings demonstrate that Cs(V_(1-x)Ta_(x))_(3)Sb_(5) with the non-trivial band topology is an excellent platform to explore the superconductivity mechanism and intertwined electronic orders in quantum materials.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 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
The recent discovery of superconductivity(SC)and charge density wave(CDW)in kagome metals AV3Sb5(A=K,Rb,Cs)provides an ideal playground for the study of emergent electronic orders.Application of moderate pressure lead...The recent discovery of superconductivity(SC)and charge density wave(CDW)in kagome metals AV3Sb5(A=K,Rb,Cs)provides an ideal playground for the study of emergent electronic orders.Application of moderate pressure leads to a two-dome-shaped SC phase regime in CsV_(3)Sb_(5) accompanied by the destabilizing of CDW phase.Nonetheless,the nature of this pressure-tuned SC state and its interplay with the CDW are yet to be explored.Here,we perform soft point-contact spectroscopy(SPCS)measurements in CsV_(3)Sb_(5) to investigate the evolution of superconducting order parameter with pressure.Surprisingly,we find that the superconducting gap is significantly enhanced between the two SC domes,at which the zero-resistance temperature is suppressed and the transition is remarkably broadened.Moreover,the temperature-dependence of the SC gap in this pressure range severely deviates from the conventional Bardeen-Cooper-Schrieffer(BCS)behavior,evidencing for strong Cooper pair phase fluctuations.These findings reveal the complex intertwining of the CDW with SC in the compressed CsV_(3)Sb_(5),suggesting striking parallel to the cuprate superconductor La2xBaxCuO4.Our results point to the essential role of charge degree of freedom in the development of intertwining electronic orders,and thus provide new constraints for theories.展开更多
Recently,competing electronic instabilities,including superconductivity and density-wave-like order,have been discovered in vanadium-based kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)with a nontrivial band topology.This find...Recently,competing electronic instabilities,including superconductivity and density-wave-like order,have been discovered in vanadium-based kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)with a nontrivial band topology.This finding stimulates considerable interest to study the interplay of these competing electronic orders and possible exotic excitations in the superconducting state.Here,we performed51V and133Cs nuclear magnetic resonance(NMR)measurements on a CsV_(3)Sb_(5)single crystal to clarify the nature of density-wave-like transition in these kagome superconductors.A first-order structural transition is unambiguously revealed below T_(s)~94 K by observing the sudden splitting of Knight shift in^(51)V NMR spectrum.Moreover,combined with^(133)Cs NMR spectrum,the present result confirms a three-dimensional structural modulation.By further analyzing the anisotropy of Knight shift and 1/T_(1)T at^(51)V nuclei,we proposed that the orbital order is the primary electronic order induced by the firstorder structural transition,which is supported by further analysis on electric field gradient at^(51)V nuclei.In addition,the evidence for possible orbital fluctuations is also revealed above T_(s).The present work sheds light on a rich orbital physics in kagome superconductors AV_(3)Sb_(5).展开更多
The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)under ambient pressure exhibit an unusual charge order,from which superconductivity emerges.In this work,by applying hydrostatic pressure using a liquid pressure medium and car...The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)under ambient pressure exhibit an unusual charge order,from which superconductivity emerges.In this work,by applying hydrostatic pressure using a liquid pressure medium and carrying out electrical resistance measurements for RbV_(3)Sb_(5),we find that the charge order becomes suppressed under a modest pressure pc(1.4 GPa<pc<1.6 GPa),while the superconducting transition temperature Tc is maximized.Tc is then gradually weakened with further increase of pressure and reaches a minimum around 14.3 GPa,before exhibiting another{maximum}around 22.8 GPa,signifying the presence of a second superconducting dome.Distinct normal state resistance anomalies are found to be associated with the second superconducting dome,similar to KV_(3)Sb_(5).Our findings point to qualitatively similar temperature-pressure phase diagrams in KV_(3)Sb_(5) and RbV_(3)Sb_(5),{and suggest a close link}between the second superconducting dome and the high-pressure resistance anomalies.展开更多
The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomen...The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomena,such as unconventional superconductivity,chiral charge density wave and electronic nematicity.These exotic quantum phases naturally leave nontrivial fingerprints in transport properties of AV3Sb5,both in electrical and thermal channels,which are prominent probes to uncover the underlying mechanisms.In this brief review,we highlight the unusual electrical and thermal transport properties observed in the unconventional charge ordered state of A V3Sb5,including giant anomalous Hall,anomalous Nernst,ambipolar Nernst and anomalous thermal Hall effects.Connections of these anomalous transport properties to time-reversal symmetry breaking,topological and multiband fermiology,as well as electronic nematicity,are also discussed.Finally,a perspective together with challenges of this rapid growing field are given.展开更多
Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors.Recently,surface-dependent vortex core states have been observed in the newly discovered kagome supercon...Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors.Recently,surface-dependent vortex core states have been observed in the newly discovered kagome superconductors CsV_(3)Sb_(5).Although the spatial distribution of the sharp zero energy conductance peak appears similar to Majorana bound states arising from the superconducting Dirac surface states,its origin remains elusive.In this study,we present observations of tunable vortex bound states(VBSs)in two chemically-doped kagome superconductors Cs(V_(1-x)Tr_(x))_(3)Sb_(5)(Tr=Ta or Ti),using low-temperature scanning tunneling microscopy/spectroscopy.The CsV_(3)Sb_(5)-derived kagome superconductors exhibit full-gap-pairing superconductivity accompanied by the absence of long-range charge orders,in contrast to pristine CsV_(3)Sb_(5).Zero-energy conductance maps demonstrate a field-driven continuous reorientation transition of the vortex lattice,suggesting multiband superconductivity.The Ta-doped CsV_(3)Sb_(5)displays the conventional cross-shaped spatial evolution of Caroli-de Gennes-Matricon bound states,while the Tidoped CsV_(3)Sb_(5)exhibits a sharp,non-split zero-bias conductance peak(ZBCP)that persists over a long distance across the vortex.The spatial evolution of the non-split ZBCP is robust against surface effects and external magnetic field but is related to the doping concentrations.Our study reveals the tunable VBSs in multiband chemically-doped CsV_(3)Sb_(5)system and offers fresh insights into previously reported Y-shaped ZBCP in a non-quantum-limit condition at the surface of kagome superconductor.展开更多
The recently discovered kagome metal series AV3Sb5(A=K, Rb, Cs) exhibits topologically nontrivial band structures, chiral charge order and superconductivity, presenting a unique platform for realizing exotic electroni...The recently discovered kagome metal series AV3Sb5(A=K, Rb, Cs) exhibits topologically nontrivial band structures, chiral charge order and superconductivity, presenting a unique platform for realizing exotic electronic states. The nature of the superconducting state and the corresponding pairing symmetry are key questions that demand experimental clarification. Here, using a technique based on the tunneling diode oscillator, the magnetic penetration depth ?λ(T) of CsV3Sb5 was measured down to 0.07 K. A clear exponential behavior in ?λ(T) with marked deviations from a T or T2 temperature dependence was observed at low temperatures, indicating an absence of nodal quasiparticles. Temperature dependence of the superfiuid density and electronic specific heat can be described by two-gap s-wave superconductivity, consistent with the presence of multiple Fermi surfaces in CsV3Sb5. These results evidence nodeless superconductivity in CsV3Sb5 under ambient pressure, and constrain the allowed pairing symmetry.展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1204100)the National Natural Science Foundation of China(Grant No.62488201)+1 种基金the Chinese Academy of Sciences(Grant Nos.XDB33030000,ZDBS-SSW-WHC001,YSBR-003,and YSBR-053)Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘The kagome superconductor CsV_(3)Sb_(5) has attracted widespread attention due to its rich correlated electron states including superconductivity, charge density wave(CDW), nematicity, and pair density wave. Notably, the modulation of the intertwined electronic orders by the chemical doping is significant to illuminate the cooperation/competition between multiple phases in kagome superconductors. In this study, we have synthesized a series of tantalum-substituted Cs(V_(1-x)Ta_(x))_(3)Sb_(5) by a modified self-flux method. Electrical transport measurements reveal that CDW is suppressed gradually and becomes undetectable as the doping content of x is over 0.07. Concurrently, the superconductivity is enhanced monotonically from T_(c) ~ 2.8 K at x = 0 to 5.2 K at x = 0.12. Intriguingly, in the absence of CDW, Cs(V_(1-x)Ta_(x))_(3)Sb_(5)(x = 0.12) crystals exhibit a pronounced two-fold symmetry of the in-plane angular-dependent magnetoresistance(AMR) in the superconducting state, indicating the anisotropic superconducting properties in the Cs(V_(1-x)Ta_(x))_(3)Sb_(5). Our findings demonstrate that Cs(V_(1-x)Ta_(x))_(3)Sb_(5) with the non-trivial band topology is an excellent platform to explore the superconductivity mechanism and intertwined electronic orders in quantum materials.
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 Natural Science Foundation of China(11888101 and 11534010)the National Key Research and Development Program of the Ministry of Science and Technology of China(2017YFA0303001 and 2019YFA0704900)+5 种基金the Anhui Initiative in Quantum Information Technologies(AHY160000)the Science Challenge Project of China(TZ2016004)the Key Research Program of Frontier Sciences,CAS,China(QYZDYSSWSLH021)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB25000000)the Collaborative Innovation Program of Hefei Science Center,CAS(2020HSC-CIP014)the Fundamental Research Funds for the Central Universities(WK3510000011).
文摘The recent discovery of superconductivity(SC)and charge density wave(CDW)in kagome metals AV3Sb5(A=K,Rb,Cs)provides an ideal playground for the study of emergent electronic orders.Application of moderate pressure leads to a two-dome-shaped SC phase regime in CsV_(3)Sb_(5) accompanied by the destabilizing of CDW phase.Nonetheless,the nature of this pressure-tuned SC state and its interplay with the CDW are yet to be explored.Here,we perform soft point-contact spectroscopy(SPCS)measurements in CsV_(3)Sb_(5) to investigate the evolution of superconducting order parameter with pressure.Surprisingly,we find that the superconducting gap is significantly enhanced between the two SC domes,at which the zero-resistance temperature is suppressed and the transition is remarkably broadened.Moreover,the temperature-dependence of the SC gap in this pressure range severely deviates from the conventional Bardeen-Cooper-Schrieffer(BCS)behavior,evidencing for strong Cooper pair phase fluctuations.These findings reveal the complex intertwining of the CDW with SC in the compressed CsV_(3)Sb_(5),suggesting striking parallel to the cuprate superconductor La2xBaxCuO4.Our results point to the essential role of charge degree of freedom in the development of intertwining electronic orders,and thus provide new constraints for theories.
基金supported by the National Key R&D Program of China(Grant Nos.2017YFA0303000,and 2016YFA0300201)the National Natural Science Foundation of China(Grant Nos.11888101,and 12034004)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB25000000)the Anhui Initiative in Quantum Information Technologies(Grant No.AHY160000)the Collaborative Innovation Program of Hefei Science Center,CAS(Grant No.2019HSCCIP007)。
文摘Recently,competing electronic instabilities,including superconductivity and density-wave-like order,have been discovered in vanadium-based kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)with a nontrivial band topology.This finding stimulates considerable interest to study the interplay of these competing electronic orders and possible exotic excitations in the superconducting state.Here,we performed51V and133Cs nuclear magnetic resonance(NMR)measurements on a CsV_(3)Sb_(5)single crystal to clarify the nature of density-wave-like transition in these kagome superconductors.A first-order structural transition is unambiguously revealed below T_(s)~94 K by observing the sudden splitting of Knight shift in^(51)V NMR spectrum.Moreover,combined with^(133)Cs NMR spectrum,the present result confirms a three-dimensional structural modulation.By further analyzing the anisotropy of Knight shift and 1/T_(1)T at^(51)V nuclei,we proposed that the orbital order is the primary electronic order induced by the firstorder structural transition,which is supported by further analysis on electric field gradient at^(51)V nuclei.In addition,the evidence for possible orbital fluctuations is also revealed above T_(s).The present work sheds light on a rich orbital physics in kagome superconductors AV_(3)Sb_(5).
基金the National Key R&D Program of China(Grant Nos.2017YFA0303100 and 2016YFA0300202)the Key R&D Program of Zhejiang Province,China(Grant No.2021C01002)+3 种基金the National Natural Science Foundation of China(Grant Nos.11974306 and 12034017)the Fundamental Research Funds for the Central Universities of Chinasupport via the UC Santa Barbara NSF Quantum Foundry funded via the Q-AMASE-i program under award DMR-1906325support from the California Nano Systems Institute through the Elings fellowship program。
文摘The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)under ambient pressure exhibit an unusual charge order,from which superconductivity emerges.In this work,by applying hydrostatic pressure using a liquid pressure medium and carrying out electrical resistance measurements for RbV_(3)Sb_(5),we find that the charge order becomes suppressed under a modest pressure pc(1.4 GPa<pc<1.6 GPa),while the superconducting transition temperature Tc is maximized.Tc is then gradually weakened with further increase of pressure and reaches a minimum around 14.3 GPa,before exhibiting another{maximum}around 22.8 GPa,signifying the presence of a second superconducting dome.Distinct normal state resistance anomalies are found to be associated with the second superconducting dome,similar to KV_(3)Sb_(5).Our findings point to qualitatively similar temperature-pressure phase diagrams in KV_(3)Sb_(5) and RbV_(3)Sb_(5),{and suggest a close link}between the second superconducting dome and the high-pressure resistance anomalies.
基金support by National Natural Science Foundation of China (Grant No. 11904040)Chongqing Research Program of Basic Research and Frontier Technology,China (Grant No. cstc2020jcyj-msxm X0263)Chinesisch-Deutsche Mobilit?tsprogamm of Chinesisch-Deutsche Zentrum für Wissenschaftsf?rderung (Grant No. M-0496)。
文摘The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomena,such as unconventional superconductivity,chiral charge density wave and electronic nematicity.These exotic quantum phases naturally leave nontrivial fingerprints in transport properties of AV3Sb5,both in electrical and thermal channels,which are prominent probes to uncover the underlying mechanisms.In this brief review,we highlight the unusual electrical and thermal transport properties observed in the unconventional charge ordered state of A V3Sb5,including giant anomalous Hall,anomalous Nernst,ambipolar Nernst and anomalous thermal Hall effects.Connections of these anomalous transport properties to time-reversal symmetry breaking,topological and multiband fermiology,as well as electronic nematicity,are also discussed.Finally,a perspective together with challenges of this rapid growing field are given.
基金supported by the National Natural Science Foundation of China(61888102,52022105,92065109,and 12174428)the National Key Research and Development Projects of China(2022YFA1204100,2018YFA0305800,2019YFA0308500,2020YFA0308800,and 2022YFA1403400)+4 种基金the CAS Project for Young Scientists in Basic Research(YSBR-003 and 2022YSBR-048)the Innovation Program of Quantum Science and Technology(2021ZD0302700)the financial support from the European Research Council(ERC Consolidator Grant “Nonlinear Topo”,No.815869)ISF-Singapore-Israel Research Grant(3520/20)supported by the US DOE,Basic Energy Sciences(DE-FG02-99ER45747)。
文摘Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors.Recently,surface-dependent vortex core states have been observed in the newly discovered kagome superconductors CsV_(3)Sb_(5).Although the spatial distribution of the sharp zero energy conductance peak appears similar to Majorana bound states arising from the superconducting Dirac surface states,its origin remains elusive.In this study,we present observations of tunable vortex bound states(VBSs)in two chemically-doped kagome superconductors Cs(V_(1-x)Tr_(x))_(3)Sb_(5)(Tr=Ta or Ti),using low-temperature scanning tunneling microscopy/spectroscopy.The CsV_(3)Sb_(5)-derived kagome superconductors exhibit full-gap-pairing superconductivity accompanied by the absence of long-range charge orders,in contrast to pristine CsV_(3)Sb_(5).Zero-energy conductance maps demonstrate a field-driven continuous reorientation transition of the vortex lattice,suggesting multiband superconductivity.The Ta-doped CsV_(3)Sb_(5)displays the conventional cross-shaped spatial evolution of Caroli-de Gennes-Matricon bound states,while the Tidoped CsV_(3)Sb_(5)exhibits a sharp,non-split zero-bias conductance peak(ZBCP)that persists over a long distance across the vortex.The spatial evolution of the non-split ZBCP is robust against surface effects and external magnetic field but is related to the doping concentrations.Our study reveals the tunable VBSs in multiband chemically-doped CsV_(3)Sb_(5)system and offers fresh insights into previously reported Y-shaped ZBCP in a non-quantum-limit condition at the surface of kagome superconductor.
基金supported by the National Key R&D Program of China (Grant Nos. 2017YFA0303100, and 2016YFA0300202)Key R&D Program of Zhejiang Province, China (Grant No. 2021C01002)National Natural Science Foundation of China (Grant Nos. 11974306, and 12034017)。
文摘The recently discovered kagome metal series AV3Sb5(A=K, Rb, Cs) exhibits topologically nontrivial band structures, chiral charge order and superconductivity, presenting a unique platform for realizing exotic electronic states. The nature of the superconducting state and the corresponding pairing symmetry are key questions that demand experimental clarification. Here, using a technique based on the tunneling diode oscillator, the magnetic penetration depth ?λ(T) of CsV3Sb5 was measured down to 0.07 K. A clear exponential behavior in ?λ(T) with marked deviations from a T or T2 temperature dependence was observed at low temperatures, indicating an absence of nodal quasiparticles. Temperature dependence of the superfiuid density and electronic specific heat can be described by two-gap s-wave superconductivity, consistent with the presence of multiple Fermi surfaces in CsV3Sb5. These results evidence nodeless superconductivity in CsV3Sb5 under ambient pressure, and constrain the allowed pairing symmetry.