Owing to the unusual geometry of kagome lattices—lattices made of corner-sharing triangles—their electrons are useful for studying the physics of frustrated, correlated and topological quantum electronic states1,2,3,4,5,6,7,8,9. In the presence of strong spin–orbit coupling, the magnetic and electronic structures of kagome lattices are further entangled, which can lead to hitherto unknown spin–orbit phenomena. Here we use a combination of vector-magnetic-field capability and scanning tunnelling microscopy to elucidate the spin–orbit nature of the kagome ferromagnet Fe3Sn2 and explore the associated exotic correlated phenomena. We discover that a many-body electronic state from the kagome lattice couples strongly to the vector field with three-dimensional anisotropy, exhibiting a magnetization-driven giant nematic (two-fold-symmetric) energy shift. Probing the fermionic quasi-particle interference reveals consistent spontaneous nematicity—a clear indication of electron correlation—and vector magnetization is capable of altering this state, thus controlling the many-body electronic symmetry. These spin-driven giant electronic responses go well beyond Zeeman physics and point to the realization of an underlying correlated magnetic topological phase. The tunability of this kagome magnet reveals a strong interplay between an externally applied field, electronic excitations and nematicity, providing new ways of controlling spin–orbit properties and exploring emergent phenomena in topological or quantum materials10,11,12.
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The data that support the findings of this study are available from the corresponding author on reasonable request.
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Experimental and theoretical work at Princeton University was supported by the Gordon and Betty Moore Foundation (GBMF4547/Hasan) and the United States Department of Energy (US DOE) under the Basic Energy Sciences programme (grant number DOE/BES DE-FG-02-05ER46200). Work at the Institute of Physics of the Chinese Academy of Science (IOP CAS) was supported by the National Key R&D Program of China (grant number 2017YFA0206303). Work at Boston College is supported by US DOE grant DE-FG02-99ER45747. We also acknowledge the Natural Science Foundation of China (grant numbers 11790313, 11774422 and 11774424), National Key R&D Program of China (numbers 2016YFA0300403 and 2017YFA0302903), the Key Research Program of the Chinese Academy of Sciences (number XDPB08-1), Princeton Center for Theoretical Science (PCTS) and Princeton Institute for the Science and Technology of Materials (PRISM)’s Imaging and Analysis Center at Princeton University. T.-R.C. was supported by the Ministry of Science and Technology under a MOST Young Scholar Fellowship (MOST Grant for the Columbus Program number 107-2636-M-006-004-), the National Cheng Kung University, Taiwan, and the National Center for Theoretical Sciences (NCTS), Taiwan. M.Z.H. acknowledges support from Lawrence Berkeley National Laboratory and the Miller Institute of Basic Research in Science at the University of California, Berkeley in the form of a Visiting Miller Professorship. We thank D. Huse and T. Neupert for discussions.
Nature thanks S. Sachdev and the other anonymous reviewer(s) for their contribution to the peer review of this work.