Plethora of tunable Weyl fermions in kagome magnet Fe3Sn2 thin films

Interplay of magnetism and electronic band topology in unconventional magnets enables the creation and fine control of novel electronic phenomena. In this work, we use scanning tunneling microscopy and spectroscopy to study thin films of a prototypical kagome magnet Fe3Sn2. Our experiments reveal an unusually large number of densely-spaced spectroscopic features straddling the Fermi level. These are consistent with signatures of low-energy Weyl fermions and associated topological Fermi arc surface states predicted by theory. By measuring their response as a function of magnetic field, we discover a pronounced evolution in energy tied to the magnetization direction. Electron scattering and interference imaging further demonstrates the tunable nature of a subset of related electronic states. Our experiments provide a direct visualization of how in-situ spin reorientation drives changes in the electronic density of states of the Weyl fermion band structure. Combined with previous reports of massive Dirac fermions, flat bands, and electronic nematicity, our work establishes Fe3Sn2 as an interesting platform that harbors an extraordinarily wide array of topological and correlated electron phenomena.

Automated summary

The interplay of magnetism and electronic band topology can create and control novel electronic phenomena in unconventional magnets. In this study, we used scanning tunneling microscopy and spectroscopy to observe unique spectroscopic features in a prototypical magnet. These features are consistent with the predicted low-energy Weyl fermions and associated topological Fermi arc surface states. By measuring their response to magnetic fields, we discovered an evolution in energy based on magnetization direction. Electron scattering and interference imaging further demonstrated the tunability of related electronic states. Our experiments directly visualize how spin reorientation affects the electronic density of states of the Weyl fermion band structure. Combined with previous research, our work establishes this magnet as an interesting platform for a wide range of topological and correlated electron phenomena.