Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes(MZMs)which could be used for topological quantum computation.Topological defects such ...Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes(MZMs)which could be used for topological quantum computation.Topological defects such as vortex lines are required to generate MZMs.Here,we observe the robust edge states along the surface steps of CaKFe_(4)As_(4).Remarkably,the tunneling spectra show a sharp zero-bias peak(ZBP)with multiple integerquantized states at the step edge under zero magnetic field.We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking.Consequently,the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters.Our results provide new insights into the interplay between topology and unconventional superconductivity,and pave a new path to generate MZMs without magnetic field.展开更多
The interplay between topology and magnetism is vital for realizing exotic quantum phenomena,significant examples including quantum anomalous Hall effect,axion insulators,and high-order topological states.These states...The interplay between topology and magnetism is vital for realizing exotic quantum phenomena,significant examples including quantum anomalous Hall effect,axion insulators,and high-order topological states.These states host great potential for future applications in high-speed and low-consumption electronic devices.Despite being extensively investigated,practical platforms are still scarce.In this work,with molecular beam epitaxy(MBE),we provide the first experimental report on high-quality Bi(110)/CrTe_(2) magnetic heterostructure.By employing in-situ high-resolution scanning tunneling microscopy,we are able to examine the interaction between magnetism and topology.There is a potential edge state at an energy level above the Fermi level,but no edge states observed near the Fermi level The absence of high-order topological corner states near EF highlights the importance of lattice matching and interface engineering in designing high-order topological states.Our study provides key insights into the interplay between two-dimensional magnetic and topological materials and offers an important dimension for engineering magnetic topological states.展开更多
We report a study of the electronic structure of BaFe_(2)As_(2) under uniaxial strains using angle-resolved photoemission spectroscopy and transport measurements. Two electron bands at the MY point, with an energy spl...We report a study of the electronic structure of BaFe_(2)As_(2) under uniaxial strains using angle-resolved photoemission spectroscopy and transport measurements. Two electron bands at the MY point, with an energy splitting of 50 meV in the strain-free sample, shift downward and merge into each other under a large uniaxial strain, while three hole bands at theГ point shift downward together. However, we also observed an enhancement of the resistance anisotropy under uniaxial strains by electrical transport measurements, implying that the applied strains strengthen the electronic nematic order in BaFe_(2)As_(2). These observations suggest that the splitting of these two electron bands at the MY point is not caused by the nematic order in BaFe_(2)As_(2).展开更多
We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inver...We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inversion in Fe1+yTexSe1-x,which explains the absence of Majorana zero modes in previous reports for Fe1+yTexSe1-xwith excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.展开更多
The iron-based superconductors(FeSCs)have recently emerged as a promising single-material Majorana platform by hosting isolated Majorana zero modes(MZMs)at relatively high temperatures.To further verify its Majorana n...The iron-based superconductors(FeSCs)have recently emerged as a promising single-material Majorana platform by hosting isolated Majorana zero modes(MZMs)at relatively high temperatures.To further verify its Majorana nature and move forward to build topological quantum qubits,it is highly desirable to achieve tunability for MZMs on homogeneous FeSCs.Here,with an in-situ strain device,we can controllably create MZMs on the homogeneous surface of stoichiometric superconductor LiFeAs by altering its chemical potential.The evolution of discrete energy modes inside a strained vortex is found to mimic exactly as the predicted topological vortex case,proving the Majorana nature of emerging zero modes of vortex.More importantly,our work provides a controllable method for MZM in a homogeneous FeSC,and such achievement of tunability of MZMs in the FeSC Majorana-material platform is an important step towards their application in topological quantum computation.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0308500)the National Natural Science Foundation of China(Grant Nos.62488201,52072401,11888101,12234016,and 12174317)+4 种基金the Chinese Academy of Sciences(Grant No.YSBR-003)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)the New Cornerstone Science Foundationthe China Postdoctoral Science Foundation(Grant No.2022M723111)the Fellowship of China National Postdoctoral Program for Innovative Talents(Grant No.BX20230358)。
文摘Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes(MZMs)which could be used for topological quantum computation.Topological defects such as vortex lines are required to generate MZMs.Here,we observe the robust edge states along the surface steps of CaKFe_(4)As_(4).Remarkably,the tunneling spectra show a sharp zero-bias peak(ZBP)with multiple integerquantized states at the step edge under zero magnetic field.We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking.Consequently,the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters.Our results provide new insights into the interplay between topology and unconventional superconductivity,and pave a new path to generate MZMs without magnetic field.
文摘The interplay between topology and magnetism is vital for realizing exotic quantum phenomena,significant examples including quantum anomalous Hall effect,axion insulators,and high-order topological states.These states host great potential for future applications in high-speed and low-consumption electronic devices.Despite being extensively investigated,practical platforms are still scarce.In this work,with molecular beam epitaxy(MBE),we provide the first experimental report on high-quality Bi(110)/CrTe_(2) magnetic heterostructure.By employing in-situ high-resolution scanning tunneling microscopy,we are able to examine the interaction between magnetism and topology.There is a potential edge state at an energy level above the Fermi level,but no edge states observed near the Fermi level The absence of high-order topological corner states near EF highlights the importance of lattice matching and interface engineering in designing high-order topological states.Our study provides key insights into the interplay between two-dimensional magnetic and topological materials and offers an important dimension for engineering magnetic topological states.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11888101 and U1832202)the Chinese Academy of Sciences (Grant Nos.QYZDB-SSWSLH043,XDB28000000,and XDB33000000)+1 种基金the K.C.Wong Education Foundation (Grant No.GJTD-2018-01)the Informatization Plan of Chinese Academy of Sciences (Grant No.CAS-WX2021SF-0102)。
文摘We report a study of the electronic structure of BaFe_(2)As_(2) under uniaxial strains using angle-resolved photoemission spectroscopy and transport measurements. Two electron bands at the MY point, with an energy splitting of 50 meV in the strain-free sample, shift downward and merge into each other under a large uniaxial strain, while three hole bands at theГ point shift downward together. However, we also observed an enhancement of the resistance anisotropy under uniaxial strains by electrical transport measurements, implying that the applied strains strengthen the electronic nematic order in BaFe_(2)As_(2). These observations suggest that the splitting of these two electron bands at the MY point is not caused by the nematic order in BaFe_(2)As_(2).
基金supported by the National Natural Science Foundation of China(Grant Nos.11888101 and U1832202)the Chinese Academy of Sciences(Grant Nos.QYZDB-SSW-SLH043,XDB28000000,and XDB33000000)+3 种基金the K.C.Wong Education Foundation(Grant No.GJTD-2018-01)the Informatization Plan of Chinese Academy of Sciences(Grant No.CAS-WX2021SF-0102)supported by the Synergetic Extreme Condition User Facility(SECUF)supported by US DOE(Grant Nos.DESC0010526 and DE-SC0012704)。
文摘We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inversion in Fe1+yTexSe1-x,which explains the absence of Majorana zero modes in previous reports for Fe1+yTexSe1-xwith excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.
基金supported by grants from the National Natural Science Foundation of China(11888101,11234014,61888102,11920101005,11921004)the Ministry of Science and Technology of China(2016YFA0202300,2018YFA0305700,2017YFA0302900,2019YFA0308500)+3 种基金the Chinese Academy of Sciences(XDB28000000,XDB07000000,112111KYSB20160061)supported by JSPS Grants-in-Aid for Scientific Research(JP19H01818,JP19H05826,JP21H04439)MEXT as the“Program for Promoting Researches on the Supercomputer Fugaku”(JPMXP1020200104)supported by the Synergic Extreme Condition User Facility,Beijing,China。
文摘The iron-based superconductors(FeSCs)have recently emerged as a promising single-material Majorana platform by hosting isolated Majorana zero modes(MZMs)at relatively high temperatures.To further verify its Majorana nature and move forward to build topological quantum qubits,it is highly desirable to achieve tunability for MZMs on homogeneous FeSCs.Here,with an in-situ strain device,we can controllably create MZMs on the homogeneous surface of stoichiometric superconductor LiFeAs by altering its chemical potential.The evolution of discrete energy modes inside a strained vortex is found to mimic exactly as the predicted topological vortex case,proving the Majorana nature of emerging zero modes of vortex.More importantly,our work provides a controllable method for MZM in a homogeneous FeSC,and such achievement of tunability of MZMs in the FeSC Majorana-material platform is an important step towards their application in topological quantum computation.
