Screening 2D materials with topological flat bands

TL;DR

This paper uses first-principles calculations to identify various 2D materials with topological flat bands near the Fermi level, providing new candidates for experimental study of flat band phenomena.

Contribution

The study systematically screens a materials database to discover 2D materials with topological flat bands, linking theoretical models to real material candidates.

Findings

Identified 2D materials with topological flat bands near the Fermi level.

Linked specific lattice structures to flat band properties.

Predicted new materials such as monolayer Nb3TeCl7 and III2VI3 compounds.

Abstract

Topological flat band (TFB) has been proposed theoretically in various lattice models, to exhibit a rich spectrum of intriguing physical behaviors. However, the experimental demonstration of flat band (FB) properties has been severely hindered by the lack of materials realization. Here, by screening materials from a first-principles materials database, we identify a group of 2D materials with TFBs near the Fermi level, covering some simple line-graph and generalized line-graph FB lattice models. These include the Kagome sublattice of O in TiO2 yielding a spin-unpolarized TFB, and that of V in ferromagnetic V3F8 yielding a spin-polarized TFB. Monolayer Nb3TeCl7 and its counterparts from element substitution are found to be breathing-Kagome-lattice crystals. The family of monolayer III2VI3 compounds exhibit a TFB representing the coloring-triangle lattice model. ReF3, MnF3 and MnBr3 are all predicted to be diatomic-Kagome-lattice crystals, with TFB transitions induced by atomic substitution. Finally, HgF2, CdF2 and ZnF2 are discovered to host dual TFBs in the diamond-octagon lattice. Our findings pave the way to further experimental exploration of eluding FB materials and properties.