Visualizing electronic nematicity tunable by magnetic field in epitaxial Kagome magnet FeSn films

Kagome lattice, a two-dimensional hexagonal network of corner-sharing triangles, hosts a plethora of quantum states arising from the interplay of topology, spin-orbit coupling, and electron correlations. In this work, we report symmetry-breaking electronic orders tunable by an applied magnetic field in a model Kagome magnet FeSn consisting of alternating stacks of two-dimensional Fe₃Sn Kagome and Sn₂ honeycomb layers. On the Fe₃Sn layer terminated FeSn thin films epitaxially grown on SrTiO₃(111) substrates by MBE, we observed trimerization of the Kagome lattice using scanning tunneling microscopy/spectroscopy, breaking its six-fold rotational symmetry while preserving the translational symmetry. Such a trimerized Kagome lattice shows an energy-dependent contrast reversal in dI/dV maps, which is significantly enhanced by bound states induced by Sn vacancy defects. This trimerized Kagome lattice also exhibits stripe modulations that are energy-dependent and tunable by an applied in-plane magnetic field, indicating symmetry-breaking nematicity from the entangled magnetic and charge degrees of freedom in antiferromagnet FeSn [Nat Commun 14, 6167 (2023)].