Fang, ShiangHan, MinyongGraff, DavidKaxiras, EfthimiosKang, MinguYe, LindaYou, Jhih-ShihLevitan, AbeFacio, JorgeJozwiak, ChrisBostwick, AaronRotenberg, EliChan, MunMcDonald, RossKaznatcheev, KonstantineVescovo, ElioBell, Davidvan den Brink, JeroenRichter, ManuelPrasad Ghimire, MadhavCheckelsky, JosephComin, Riccardo2019-12-302019-12-09Kang, Mingu, Linda Ye, Shiang Fang, Jhih-Shih You, Abe Levitan, Minyong Han, Jorge I. Facio, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Mun K. Chan, Ross D McDonald, David Graf, Konstantine Kaznatcheev, Elio Vescovo, David C. Bell, Efthimios Kaxiras, Jeroen Van Den Brink, Manuel Richter, Madhav Prasad Ghimire, Joseph G. Checkelsky, and Riccardo Comin. 2019. Dirac Fermions and Flat Bands in the Ideal Kagome Metal FeSn. Nature Materials.1476-11221476-4660http://nrs.harvard.edu/urn-3:HUL.InstRepos:42083020A kagome lattice of 3d transition metal ions is a versatile platform for correlated topological phases hosting symmetry-protected electronic excitations and magnetic ground states. However, the paradigmatic states of the idealized two-dimensional kagome lattice – Dirac fermions and flat bands – have not been simultaneously observed. Here, we utilize angle-resolved photoemission spectroscopy and de Haas-van Alphen quantum oscillations to reveal coexisting surface and bulk Dirac fermions as well as flat bands in the antiferromagnetic kagome metal FeSn, that has spatially-decoupled kagome planes. Our band structure calculations and matrix element simulations demonstrate that the bulk Dirac bands arise from in-plane localized Fe-3d orbitals, and evidence that coexisting Dirac surface state realizes a rare example of fully spin-polarized two-dimensional Dirac fermions due to spin-layer locking in FeSn. The prospect to harness these prototypical excitations in kagome lattice is a frontier of great promise at the confluence of topology, magnetism, and strongly-correlated physics.en-USMechanical EngineeringGeneral Materials ScienceMechanics of MaterialsGeneral ChemistryCondensed Matter PhysicsJournal Article2019-12-3010.1038/s41563-019-0531-0