Visualizing symmetry-breaking electronic orders in epitaxial Kagome antiferromagnet FeSn films

The Kagome lattice is a unique geometric structure composed of interlaced triangles, where each lattice point has four neighboring points. This distinctive arrangement gives rise to various quantum states emergent from the interplay of frustration, spin-orbit coupling, and electron correlations. In this talk, I will present our recent work on the epitaxial growth and atomic resolution imaging of symmetry-breaking electronic orders in a model Kagome antiferromagnet FeSn. Earlier studies on FeSn have primarily focused on bulk materials; here, we synthesized high-quality FeSn thin films on SrTiO3(111) substrates using molecular beam epitaxy. The FeSn crystal structure consists of alternating planes of Fe₃Sn Kagome and Sn honeycomb lattices, which are revealed by our in-situ low-temperature scanning tunneling microscopy. Interestingly, we observed stripe modulations in the electronic structure of the Fe3Sn Kagome layer that can be tuned by an in-plane magnetic field, indicating a nematic electronic order that breaks its 6-fold rotational symmetry. Additionally, we imaged bound states of Sn vacancy defects and observed anomalous magnetic field dependence. Near the single Sn-vacancy on the Fe3Sn Kagome layer, anisotropic quasiparticle interference patterns are observed in the differential conductance dI/dV maps, consistent with the symmetry-breaking nematic electronic states. Under an out-of-plane magnetic field, anomalous Zeeman shifts are seen, where their energy blue shifts independent of the field direction. Under an in-plane magnetic field, the shift of the bound state energy shows a two-fold oscillating behavior as a function of the azimuth angle. These results provide insight into symmetry-breaking electronic orders arising from the entangled magnetic and charge degrees of freedom in magnetic Kagome materials.