Electronic instabilities of kagome metals: saddle points and Landau theory

TL;DR

This paper investigates electronic instabilities in kagome metals near saddle points, identifying various density wave orders and their implications for charge density wave phenomena, using renormalization group and Landau theory methods.

Contribution

It combines parquet renormalization group analysis with Landau theory to elucidate the mechanisms behind charge density waves in kagome metals.

Findings

Superconducting, charge, orbital moment, and spin density wave instabilities identified.

Charge density wave modulations explained via primary density wave orders.

Provides constraints on charge ordering mechanisms in AV$_3$Sb$_5$ family.

Abstract

We study electronic instabilities of a kagome metal with a Fermi energy close to saddle points at the hexagonal Brillouin zone face centers. Using parquet renormalization group, we determine the leading and subleading instabilities, finding superconducting, charge, orbital moment, and spin density waves. We then derive and use Landau theory to discuss how different primary density wave orders give rise to charge density wave modulations, as seen in the AV$_3$Sb$_5$ family, with A=K,Rb,Cs. The results provide strong constraints on the mechanism of charge ordering and how it can be further refined from existing and future experiments.