Epitaxial Kagome Thin Films as a Platform for Topological Flat Bands

TL;DR

This paper reports the successful growth and characterization of epitaxial CoSn kagome thin films, demonstrating flat bands near the Fermi level, which are crucial for exploring strongly correlated electronic phenomena.

Contribution

It presents the first direct observation of flat bands in epitaxial kagome CoSn thin films and confirms their band structure aligns with theoretical predictions.

Findings

Flat bands observed via ARPES in epitaxial CoSn films

Band structure matches DFT calculations

Transport properties explained by band and semiclassical theory

Abstract

Systems with flat bands are ideal for studying strongly correlated electronic states and related phenomena. Among them, kagome-structured metals such as CoSn have been recognized as promising candidates due to the proximity between the flat bands and the Fermi level. A key next step will be to realize epitaxial kagome thin films with flat bands to enable tuning of the flat bands across the Fermi level via electrostatic gating or strain. Here we report the band structures of epitaxial CoSn thin films grown directly on insulating substrates. Flat bands are observed using synchrotron-based angle-resolved photoemission spectroscopy (ARPES). The band structure is consistent with density functional theory (DFT) calculations, and the transport properties are quantitatively explained by the band structure and semiclassical transport theory. Our work paves the way to realize flat band-induced phenomena through fine-tuning of flat bands in kagome materials.