[Professor Kang’s research team] World’s First Realization of ‘Kagomene’, a Two-Dimensional Material Hosting ‘Infinitely Massive Electrons’ (published in Nature Physics)
Kagome lattice materials host a variety of intriguing quantum phenomena arising from the intrinsic interplay of topology, electron correlations and geometric frustration. Even though previous studies have primarily focused on bulk three-dimensional kagome materials, the realization of an ideal two-dimensional kagome system has remained a long-standing goal. Here we demonstrate ideal two-dimensional monolayer kagome lattices in the van der Waals material family A2T3X4, where A is an alkali metal, T is a transition metal and X is a chalcogen. Our nanofocused angle-resolved photoemission spectroscopy directly characterizes the electronic structure of A2T3X4 down to the monolayer limit, revealing an isolated kagome-derived flat band just below the Fermi level. Through electrostatic gating, the kagome flat band can be further tuned to the Fermi level, enabling direct access to partially filled flat-band physics. Compared with existing moiré-based artificial flat-band systems, this monolayer kagome platform realizes more than 220-fold higher flat-band electron density, offering opportunities to explore emergent flat-band phenomena at temperatures higher than those currently achievable.
Authors: Hyungkun Bong (first author), Sehyun Oh, Jiyong Han, Hyunjong Lee, Jinhyeok Choi, Mingu Kang (corresponding author)