Vacuum ultraviolet(VUV)lasers have demonstrated great potential as the light source for various spectroscopies,which,if they can be focused into a small beam spot,will not only allow investigation of mesoscopic materi...Vacuum ultraviolet(VUV)lasers have demonstrated great potential as the light source for various spectroscopies,which,if they can be focused into a small beam spot,will not only allow investigation of mesoscopic materials and structures but also find application in the manufacture of nano-objects with excellent precision.In this work,we report the construction of a 177 nm VUV laser that can achieve a record-small(〜0.76 μm)focal spot at a long focal length(~45 mm)by using a flat lens without spherical aberration.The size of the beam spot of this VUV laser was tested using a metal grating and exfoliated graphene flakes,and we demonstrated its application in a fluorescence spectroscopy study on pure and Tm3+-doped NaYF4 microcrystals,revealing a new emission band that cannot be observed in the traditional up-conversion process.In addition,this laser system would be an ideal light source for spatially and angleresolved photoemission spectroscopy.展开更多
Magnetic topological quantum materials(TQMs) provide a fertile ground for the emergence of fascinating topological magneto-electric effects. Recently, the discovery of intrinsic antiferromagnetic(AFM) topological insu...Magnetic topological quantum materials(TQMs) provide a fertile ground for the emergence of fascinating topological magneto-electric effects. Recently, the discovery of intrinsic antiferromagnetic(AFM) topological insulator MnBi_(2)Te_(4) that could realize quantized anomalous Hall effect and axion insulator phase ignited intensive study on this family of TQM compounds. Here, we investigated the AFM compound Mn Bi4 Te7 where Bi_(2)Te_(3) and MnBi_(2)Te_(4) layers alternate to form a superlattice. Using spatial-and angleresolved photoemission spectroscopy, we identified ubiquitous(albeit termination dependent) topological electronic structures from both Bi_(2)Te_(3) and MnBi_(2)Te_(4) terminations. Unexpectedly, while the bulk bands show strong temperature dependence correlated with the AFM transition, the topological surface states with a diminishing gap show negligible temperature dependence across the AFM transition.Together with the results of its sister compound MnBi_(2)Te_(4), we illustrate important aspects of electronic structures and the effect of magnetic ordering in this family of magnetic TQMs.展开更多
Gérard Mourou received his PhD from Pierre and Marie Curie University in 1973.He and his student Donna Strickland co-invented chirped pulse amplification(CPA)technology and shared the 2018 Nobel Prize in Physics....Gérard Mourou received his PhD from Pierre and Marie Curie University in 1973.He and his student Donna Strickland co-invented chirped pulse amplification(CPA)technology and shared the 2018 Nobel Prize in Physics.This technology made it possible to apply ultrafast lasers to many new areas,such as eye surgery,precision manufacturing,particle physics and nuclear fusion.Gérard Mourou is the founding Director of the Center for Ultrafast Optical Science(CUOS)at the University of Michigan and the initiator of the Extreme Light Infrastructure(ELI)in Europe.展开更多
基金C.Z.,L.Y.,and K.H.acknowledge support from the National Natural Science Foundation of China(grants 11774427,61875181,61705085,11774190,and 11427903)Y.C.acknowledges support from the Engineering and Physical Sciences Research Council Platform(grant EP/M020517/1)+1 种基金K.H.thanks USTC Research Funds of the Double Rrst-Class Initiative(grant YD2030002003)"the Fundamental Research Funds for the Central Universities"in China,the CAS Pioneer Hundred Talents Program,and the support from the University of Science and Technology of China’s Centre for Micro and Nanoscale Research and Fabrication.
文摘Vacuum ultraviolet(VUV)lasers have demonstrated great potential as the light source for various spectroscopies,which,if they can be focused into a small beam spot,will not only allow investigation of mesoscopic materials and structures but also find application in the manufacture of nano-objects with excellent precision.In this work,we report the construction of a 177 nm VUV laser that can achieve a record-small(〜0.76 μm)focal spot at a long focal length(~45 mm)by using a flat lens without spherical aberration.The size of the beam spot of this VUV laser was tested using a metal grating and exfoliated graphene flakes,and we demonstrated its application in a fluorescence spectroscopy study on pure and Tm3+-doped NaYF4 microcrystals,revealing a new emission band that cannot be observed in the traditional up-conversion process.In addition,this laser system would be an ideal light source for spatially and angleresolved photoemission spectroscopy.
基金supported by the National Key Research and Development Program of China (2017YFA0305400, 2017YFA0304600, 2018YFA0307100, and 2018YFA0305603)the National Natural Science Foundation of China (11774190, 11674229, 11634009, 11774427, 51788104, and 11874035)+1 种基金EPSRC Platform Grant (EP/M020517/1)the support from the Shanghai Pujiang Program (17PJ1406200)。
文摘Magnetic topological quantum materials(TQMs) provide a fertile ground for the emergence of fascinating topological magneto-electric effects. Recently, the discovery of intrinsic antiferromagnetic(AFM) topological insulator MnBi_(2)Te_(4) that could realize quantized anomalous Hall effect and axion insulator phase ignited intensive study on this family of TQM compounds. Here, we investigated the AFM compound Mn Bi4 Te7 where Bi_(2)Te_(3) and MnBi_(2)Te_(4) layers alternate to form a superlattice. Using spatial-and angleresolved photoemission spectroscopy, we identified ubiquitous(albeit termination dependent) topological electronic structures from both Bi_(2)Te_(3) and MnBi_(2)Te_(4) terminations. Unexpectedly, while the bulk bands show strong temperature dependence correlated with the AFM transition, the topological surface states with a diminishing gap show negligible temperature dependence across the AFM transition.Together with the results of its sister compound MnBi_(2)Te_(4), we illustrate important aspects of electronic structures and the effect of magnetic ordering in this family of magnetic TQMs.
文摘Gérard Mourou received his PhD from Pierre and Marie Curie University in 1973.He and his student Donna Strickland co-invented chirped pulse amplification(CPA)technology and shared the 2018 Nobel Prize in Physics.This technology made it possible to apply ultrafast lasers to many new areas,such as eye surgery,precision manufacturing,particle physics and nuclear fusion.Gérard Mourou is the founding Director of the Center for Ultrafast Optical Science(CUOS)at the University of Michigan and the initiator of the Extreme Light Infrastructure(ELI)in Europe.
