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The kagome network, very popular in Japanese art, is one of the possible tilings of two-dimensional space, one with the same point symmetries as the hexagonal lattice of graphene. Recent theoretical developments suggest that the combination of unusual magnetism, spin-orbit coupling, and geometric frustration in kagome metals may lead to a wide range of novel topological physics, such as fractional quantum Hall effect and intrinsic anomalous Hall effect. In these phenomena, a major role is played by the topologically nontrivial flat bands and massive Dirac cones, both of which are predicted to exist from the unique geometrical hopping pathways of kagome lattice. Despite these predictions, the experimental band structure of kagome compounds has long remained unreported.
In this talk, I will report on the experimental band structure of various kagome compounds belonging to the family of transition metal stannides, and in particular Fe3Sn2, FeSn, and CoSn. In these systems which intertwine robust magnetism and electronic topology, we observed various manifestations of topological physics. These include the realization of the Kane-Mele model for 2D Dirac fermions with a spin-orbit-induced topological gap, as well as the discovery of the elusive flat bands with nonzero Chern number.
In sum, transition metal-based kagome lattices have emerged a new platform for intriguing phenomena arising from the combination of topology, magnetism, and correlations. I will discuss the prospects and outlook for further exploration of novel topological physics in this materials family.
Prof. Riccardo Comin received his PhD in Physics degree from University of British Columbia, Canada in 2013. After his PhD study, Riccardo moved to University of Toronto for a postdoctoral position for another two years. In 2016, Riccardo joined the Department of Physics, Massachusetts Institute of Technology (MIT) as an Assistant Professor, where he set up his research group to study the emergent phenomena in quantum materials in both the crystalline and thin-film form, using a wide range of photon techniques (resonant X-ray scattering and diffraction, inelastic scattering, and time-resolved photon scattering, etc).
Riccardo has received a number of prestigious awards due to his outstanding research achievements. These include: Sloan Fellowship, awarded by the Sloan Foundation (2018), Canadian Light Source Young Investigator Award (2017), Bryan R. Coles Prize, awarded by the International Conference on Strongly Correlated Electron Systems (2016), McMillan Award, awarded by the University of Illinois Urbana-Champaign (2015), John Charles Polanyi Prize in Physics, awarded by the Council of Ontario Universities (2015), Fonda-Fasella Award, awarded by the Italian Light Source Elettra (2014), G. Bancroft Ph.D. Thesis Award, awarded by the Canadian Light Source (05/2014), and more.
Venue: TDLI Meeting Room 200
Here is the Zoom link if you prefer to join us remotely:
https://zoom.com.cn/j/97870649629
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