The kagome metal FeGe provides a rich platform for understanding the mechanisms behind competing orders,as it exhibits charge order(CO)emerging deep within the antiferromagnetic phase.To investigate the intrinsic orig...The kagome metal FeGe provides a rich platform for understanding the mechanisms behind competing orders,as it exhibits charge order(CO)emerging deep within the antiferromagnetic phase.To investigate the intrinsic origin of this behavior,we examine the evolution of the low-energy electronic structure across the phase transition in annealed FeGe samples using angleresolved photoemission spectroscopy.We find no evidence supporting a conventional nesting mechanism,such as Fermi surface nesting or van Hove singularities.However,we observe two notable changes in the band structure:an electron-like band around the K point and another around the A point,both shifting upward in energy when CO forms.These findings are consistent with our density-functional theory calculations,which suggest that the charge order in FeGe is primarily driven by magnetic energy savings due to a lattice distortion involving Ge1-dimerization.Our results provide photoemission evidence supporting this novel mechanism for CO formation in FeGe,in contrast to the conventional nesting-driven mechanisms.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
基金supported by the National Natural Science Foundation of China(Grant Nos.12174362,11888101,11790312,92065202,12474142,and 12174365)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302803)the New Cornerstone Science Foundation.Part of this research used Beamline 03U of the Shanghai Synchrotron Radiation Facility,which is supported by the ME2 project from the National Natural Science Foundation of China(Grant No.11227902).
文摘The kagome metal FeGe provides a rich platform for understanding the mechanisms behind competing orders,as it exhibits charge order(CO)emerging deep within the antiferromagnetic phase.To investigate the intrinsic origin of this behavior,we examine the evolution of the low-energy electronic structure across the phase transition in annealed FeGe samples using angleresolved photoemission spectroscopy.We find no evidence supporting a conventional nesting mechanism,such as Fermi surface nesting or van Hove singularities.However,we observe two notable changes in the band structure:an electron-like band around the K point and another around the A point,both shifting upward in energy when CO forms.These findings are consistent with our density-functional theory calculations,which suggest that the charge order in FeGe is primarily driven by magnetic energy savings due to a lattice distortion involving Ge1-dimerization.Our results provide photoemission evidence supporting this novel mechanism for CO formation in FeGe,in contrast to the conventional nesting-driven mechanisms.
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.
