Fantastic flat bands and where to find them: The CoSn-type compounds

TL;DR

This paper investigates CoSn-type compounds with kagome lattice structures, identifying flat bands at the Fermi level and highlighting CoSn and RhPb as promising candidates for studying flat band physics and strong electron correlations.

Contribution

It characterizes flat bands in six CoSn-type compounds and proposes CoSn and RhPb as key materials for flat band physics research.

Findings

Flat bands are present in CoSn-type compounds with kagome lattice.

CoSn and RhPb are identified as promising materials for flat band physics.

Iron variants are antiferromagnetic and thus less suitable for flat band studies.

Abstract

Quantum interference on the kagome lattice generates electronic bands with narrow bandwidth, called flat bands. Crystal structures incorporating this lattice can host strong electron correlations with non-standard ingredients, but only if these bands lie at the Fermi level. In the six compounds with the CoSn structure type (FeGe, FeSn, CoSn, NiIn, RhPb, and PtTl) the transition metals form a kagome lattice. The two iron variants are robust antiferromagnets so we focus on the latter four and investigate their thermodynamic and transport properties. We consider these results and calculated band structures to locate and characterize the flat bands in these materials. We propose that CoSn and RhPb deserve the community's attention for exploring flat band physics.