Finite-Temperature Ferromagnetic Correlations of the Kagome Lattice Hubbard Model

TL;DR

This study uses advanced finite-temperature methods to analyze ferromagnetic correlations in the Kagome lattice Hubbard model, revealing how interactions influence magnetic properties and the metal-insulator transition.

Contribution

It provides new insights into ferromagnetic correlations and the metal-insulator transition in the Kagome lattice Hubbard model using exact finite-temperature techniques.

Findings

Repulsive interactions enhance ferromagnetic correlations at high electron densities.

Increasing interaction strength extends ferromagnetic regions towards half filling.

Charge compressibility estimates the critical interaction for the metal-insulator transition.

Abstract

The Kagome lattice Fermi-Hubbard model is one of the most physically rich, and at the same time most challenging, models to study in strongly-correlated physics. Among its special features are geometric frustration and a flat energy band that create conditions favorable to ferromagnetism near the band insulating limit. Here, we utilize two exact finite-temperature methods, the numerical linked-cluster expansion and the determinant quantum Monte Carlo, to study the extent as well as doping and interaction dependence of ferromagnetic correlations and other thermodynamic properties of the model. We find that repulsive interactions enhance ferromagnetic correlations at high electron densities and that increasing the interaction strength, extends the region with strong ferromagnetic correlations towards half filling, smoothly connecting it to Nagaoka ferromagnetism near the Mott insulating region. We also use the charge compressibility to obtain an accurate estimate for the critical interaction strength for the metal-insulator transition at half filling. These results improve our understanding of the magnetic tendencies of the model away from half filling and pave the way for further studies, including with ultracold atoms in optical lattices.