Unconventional Fermi surface instabilities in the Kagome Hubbard Model

TL;DR

This paper explores various unconventional Fermi surface instabilities in the Kagome Hubbard model near van Hove filling, revealing complex interplay between magnetic, density wave, and superconducting orders using advanced theoretical methods.

Contribution

It introduces a comprehensive analysis of competing instabilities in the Kagome Hubbard model, highlighting the role of sublattice interference and functional renormalization group techniques.

Findings

Identification of finite angular momentum density waves.

Discovery of a two-fold degenerate d-wave Pomeranchuk instability.

Observation of f-wave superconductivity away from van Hove filling.

Abstract

We investigate the competing Fermi surface instabilities in the Kagome tight-binding model. Specifically, we consider onsite and short-range Hubbard interactions in the vicinity of van Hove filling of the dispersive Kagome bands where the Fermiology promotes the joint effect of enlarged density of states and nesting. The sublattice interference mechanism [Kiesel and Thomale, Phys. Rev. B Rapid Comm., in press.] allows us to explain the intricate interplay between ferromagnetic fluctuations and other ordering tendencies. On the basis of functional renormalization group used to obtain an adequate low-energy theory description, we discover finite angular momentum spin and charge density wave order, a two-fold degenerate d-wave Pomeranchuk instability, and f-wave superconductivity away from van Hove filling. Together, this makes the Kagome Hubbard model the prototypical scenario for several unconventional Fermi surface instabilities.