Origin of correlated isolated flat bands in copper-substituted lead phosphate apatite

TL;DR

This paper uses density functional theory to identify correlated flat bands in Cu-substituted lead phosphate apatite, linking structural distortions and charge density waves to potential high-temperature superconductivity.

Contribution

It reveals the origin of flat bands in Cu-doped apatite and proposes a minimal two-band model for its low-energy physics.

Findings

Correlated flat bands are present at the Fermi level.

Structural distortion and chiral charge density wave cause these bands.

Implications for potential superconductivity in Cu-doped apatite.

Abstract

A recent report of room temperature superconductivity at ambient pressure in Cu-substituted apatite (`LK99') has invigorated interest in the understanding of what materials and mechanisms can allow for high-temperature superconductivity. Here I perform density functional theory calculations on Cu-substituted lead phosphate apatite, identifying correlated isolated flat bands at the Fermi level, a common signature of high transition temperatures in already established families of superconductors. I elucidate the origins of these isolated bands as arising from a structural distortion induced by the Cu ions and a chiral charge density wave from the Pb lone pairs. These results suggest that a minimal two-band model can encompass much of the low-energy physics in this system. Finally, I discuss the implications of my results on possible superconductivity in Cu-doped apatite.