Evidence of high electron mobility in magnetic Kagome metal FeSn thin films

The Kagome lattice due to its peculiar geometry, in conjunction with crystal symmetries and spin-orbit coupling, provides an ideal playground to investigate emerging electronic excitations associated with novel topological phases. Moreover, this lattice structure gives rise to exotic magnetic properties, including frustration and spin-liquid phases, whose interplay with topology is incredibly promising for the realisation of innovative transport properties suitable for spintronic devices. This complex picture can be further enriched if, at variance with the usual s or p orbital-based topological systems, binary and ternary intermetallic compounds are introduced to populate the kagome network with low energy 3d electrons, providing a platform to study the interplay between electronic topology and strong correlations. Here we present a systematic study of the low-energy electrodynamics of the magnetic FeSn Kagome metal, which host the fingerprints of the 2D Kagome systems, i.e. Dirac states and flat bands. Our results reveal that the optical conductivity of FeSn shows two Drude contributions that can be linked to the linear (Dirac) and parabolic (massive) bands, with a dominance of the former to the DC conductivity at low temperatures. The weight of the Drude response shifts toward lower frequencies upon cooling due to a rapid increase in the Dirac electrons mobility, which we associate to a temperature suppression of e-ph scattering. The experimental interband conductivity is in very good agreement with that calculated by density functional theory (DFT). These results provide a full description of the charge-dynamics in FeSn Kagome metal.