Robust flat bands in RCo5 (R=rare earth) compounds

TL;DR

This paper clarifies the origin of flat bands in RCo5 compounds through first-principles and tight-binding models, showing they arise from localized states due to partial cancellation of hopping amplitudes, and discusses flat-band engineering possibilities.

Contribution

It provides a detailed mechanism for flat band formation in RCo5 compounds and demonstrates how their positions can be tuned via lattice parameter adjustments.

Findings

Flat bands originate from localized eigenstates due to partial cancellation of hopping.

The relative position of flat bands can be controlled by lattice parameter variation.

Flat bands remain nearly dispersionless despite lattice modifications.

Abstract

The mechanism to realize the peculiar flat bands generally existing in RCo5 (R=rare earth) compounds is clarified by analyzing the first-principles band structures and the tight-binding model. These flat bands are constructed from the localized eigenstates, the existence of which is guaranteed by the partial cancelation between the intersite hopping amplitudes among the Co-3d states at the Kagome sites and those between the Kagome and honeycomb sites. Their relative positions to other bands can be controlled by varying the lattice parameters keeping their dispersion almost flat, which suggests the possibility of flat-band engineering.