Realisation of epitaxial ultra-thin Kagome metal FeSn films

Abstract

Kagome metals, a new class of metal, have recently attracted significant attention due to their rich topological, strong electron-correlated and magnetic properties. These properties arise from the corner-sharing, triangular geometry that can facilitate both Dirac bands (massless electrons) and flat bands (massive electrons). The quantum anomalous hall effect (QAHE) and fractional-QAHE are believed to exist in 2D-isolated Kagome layers with spin-orbit coupling, leading to promising applications in ultra-low energy electronics and quantum computing. Though high-quality thin Kagome metal films have been realised, such as >20nm FeSn and Mn3Sn, large-area ultra-thin films have yet to be reported. Here, we report the successful growth of high-quality epitaxial ultra-thin FeSn films (<10nm) via molecular beam epitaxy. Structural characterisation reveals the Kagome lattice, with the expected lattice constant and correct 1:1 stoichiometry by X-ray photo-emission spectroscopy (XPS). Angular resolved photo-emission spectroscopy (ARPES) measurements confirm the existence of Dirac bands at the K-points in the Brillouin Zone, where the extracted Fermi velocity of 1.3 × 105 ms- 1 is consistent with bulk FeSn measurements. The successful growth of ultra-thin Kagome metal films provides a pathway towards understanding the effect of quantum confinement on the electronic band structure, in particular, the opening of a bandgap in the Dirac bands and the realisation of novel quantum phenomena.