Topological flat bands emerging at the inversion of stacking order in rhombohedral graphite

TL;DR

This study investigates how stacking order modifications in rhombohedral graphite can lead to topologically protected flat bands near the Fermi level, potentially related to high-temperature superconductivity.

Contribution

It reveals the emergence of topological flat bands at interfaces of different stacking configurations using first-principles calculations and a simplified tight-binding model.

Findings

Flat bands appear at interfaces between different stacking orders.

Topological origin of flat bands is confirmed.

Mapping to SSH model clarifies the physics behind flat band emergence.

Abstract

Motivated by the indications of high-Tc superconductivity in natural graphite enriched in the rhombohedral phase, we study the band structure of several stacking configurations that combine two of the three graphite structures as well as modifications of the rhombohedral sequence (from ABCABC... to CBACBA...), using first-principles calculations. We focus in particular on the possible emergence of flat bands near the Fermi level. When the two different rhombohedral orderings are combined, flat bands of topological origin emerge at the interface between the two domains, near the K and K' points of the Brillouin zone. Mapping a simple tight-binding model of a rhombohedral slab along the direction perpendicular to the graphene layers onto a Su-Schrieffer-Heeger chain provides a transparent understanding of the underlying physics.