Highly Tunable Electronic Structures in Kagome Magnet Fe_xSn_y Thin Films

The kagome lattice is a corner-sharing triangular lattice that hosts flat bands, van Hove singularities and Dirac crossings. Recent experimental discoveries in kagome metals have showcased that they are an excellent platform for studying emergent charge, magnetic, superconducting orders as well as topological electronic structures. Fe_xSn_y (Fe₃Sn₂ and FeSn) has been shown to exhibit (massive) Dirac fermions, anomalous Hall effect, flat bands and more. Here, we selectively synthesize Fe₃Sn₂ and FeSn thin films using molecular beam epitaxy. In Fe₃Sn₂, using spectroscopic-imaging scanning tunneling microscopy, we discover a number of dI/dV spectral peaks. These peaks show a prominent magnetic-field-tunability. The features point to the theoretically-predicted tunable Weyl points near the Fermi level. In FeSn, we use angle-resolved photoemission spectroscopy to resolve the band structure, which is significantly tunable as we change the temperature of the sample. Our findings suggest highly tunable electronic structures in the kagome magnet Fe_xSn_y thin films.