High-Order Van Hove Singularities in Atomically Thin Kagome Metal LaTl₃.

Abstract

Kagome materials serve as a versatile platform where an interplay of flat bands, Dirac Fermions, and Van Hove singularities enables the emergence of exotic strongly correlated phenomena. Recently, it was predicted that an ideal single layer kagome lattice may host high-order Van Hove singularities (HOVHSs) characterized by extremely flat dispersions, leading to drastic changes in electronic behavior. However, experimentally, HOVHSs have been observed up to now only in a narrow range of materials, mostly in graphene layers, but not in metal-semiconductor interfaces. Here, we report the discovery of HOVHSs in the monolayer-thick kagome metal LaTl₃ epitaxially synthesized on the Si(111) substrate. The scanning tunneling microscopy observations and ab initio calculations indicate the kagome-like ordering of the LaTl₃ layer, while the angle-resolved photoemission spectroscopy measurements and theoretical predictions uncover a rich and complex landscape of various Van Hove singularities emerged in the system, including high-order ones, which can significantly affect the anomalous Hall response and enable the unique high electron-correlation regime in the system. The discovered properties make the LaTl₃ kagome monolayer a highly attractive material for ultracompact nanoelectronic devices.