Persistent flat band splitting and strong selective band renormalization in a kagome magnet thin film

Zheng Ren, Jianwei Huang, Hengxin Tan, Ananya Biswas, Aki Pulkkinen, Yichen Zhang, Yaofeng Xie, Ziqin Yue, Lei Chen, Fang Xie, Kevin Allen, Han Wu, Qirui Ren, Anil Rajapitamahuni, Asish K. Kundu, Elio Vescovo, Junichiro Kono, Emilia Morosan, Pengcheng Dai, Jian-Xin Zhu, Qimiao Si, Ján Minár, Binghai Yan and Ming Yi ()
Additional contact information
Zheng Ren: Rice University
Jianwei Huang: Rice University
Hengxin Tan: Weizmann Institute of Science
Ananya Biswas: Rice University
Aki Pulkkinen: University of West Bohemia
Yichen Zhang: Rice University
Yaofeng Xie: Rice University
Ziqin Yue: Rice University
Lei Chen: Rice University
Fang Xie: Rice University
Kevin Allen: Rice University
Han Wu: Rice University
Qirui Ren: Rice University
Anil Rajapitamahuni: Brookhaven National Lab
Asish K. Kundu: Brookhaven National Lab
Elio Vescovo: Brookhaven National Lab
Junichiro Kono: Rice University
Emilia Morosan: Rice University
Pengcheng Dai: Rice University
Jian-Xin Zhu: Los Alamos National Laboratory
Qimiao Si: Rice University
Ján Minár: University of West Bohemia
Binghai Yan: Weizmann Institute of Science
Ming Yi: Rice University

Nature Communications, 2024, vol. 15, issue 1, 1-9

Abstract: Abstract Magnetic kagome materials provide a fascinating playground for exploring the interplay of magnetism, correlation and topology. Many magnetic kagome systems have been reported including the binary FemXn (X = Sn, Ge; m:n = 3:1, 3:2, 1:1) family and the rare earth RMn6Sn6 (R = rare earth) family, where their kagome flat bands are calculated to be near the Fermi level in the paramagnetic phase. While partially filling a kagome flat band is predicted to give rise to a Stoner-type ferromagnetism, experimental visualization of the magnetic splitting across the ordering temperature has not been reported for any of these systems due to the high ordering temperatures, hence leaving the nature of magnetism in kagome magnets an open question. Here, we probe the electronic structure with angle-resolved photoemission spectroscopy in a kagome magnet thin film FeSn synthesized using molecular beam epitaxy. We identify the exchange-split kagome flat bands, whose splitting persists above the magnetic ordering temperature, indicative of a local moment picture. Such local moments in the presence of the topological flat band are consistent with the compact molecular orbitals predicted in theory. We further observe a large spin-orbital selective band renormalization in the Fe $${{{{\rm{d}}}}}_{{xy}}+{{{{\rm{d}}}}}_{{x}^{2}-{y}^{2}}$$ d x y + d x 2 − y 2 spin majority channel reminiscent of the orbital selective correlation effects in the iron-based superconductors. Our discovery of the coexistence of local moments with topological flat bands in a kagome system echoes similar findings in magic-angle twisted bilayer graphene, and provides a basis for theoretical effort towards modeling correlation effects in magnetic flat band systems.

Date: 2024
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DOI: 10.1038/s41467-024-53722-3

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