Magnetic fluctuations near the Van Hove singularity in the kagome-lattice Hubbard model at finite doping

TL;DR

This study uses quantum Monte Carlo simulations to explore how magnetic fluctuations in the kagome-lattice Hubbard model are influenced by the Van Hove singularity, revealing tendencies toward ferromagnetism at finite doping.

Contribution

It provides the first systematic analysis of magnetic susceptibility near the Van Hove singularity in the kagome Hubbard model using determinant quantum Monte Carlo.

Findings

Ferromagnetic fluctuations dominate beyond the Van Hove point.

Magnetic susceptibility increases with interaction strength and decreasing temperature.

Finite-size analysis suggests possible finite-temperature ferromagnetic phase.

Abstract

The kagome-lattice Hubbard model attracts widespread interest due to its flat-band and Van Hove singularity features, which can give rise to unconventional magnetism. We employ determinant quantum Monte Carlo simulations to systematically investigate the uniform magnetic susceptibility across a range of on-site interactions and electron fillings on a two-dimensional kagome lattice. Beyond the Van Hove singularity, dominant ferromagnetic fluctuations emerge. Magnetic susceptibility grows markedly with increasing interaction strength and decreasing temperature, indicating that the Van Hove singularity acts as a critical point for the crossover of dominant magnetic fluctuations. Finite-size analysis further suggests the potential stabilization of a finite-temperature ferromagnetic phase. We also examine the sign problem to identify numerically reliable parameter regimes. These results provide valuable insights into controlling magnetic fluctuations in kagome systems and establish a computational framework for exploring flat-band physics in regimes characterized by novel quantum phases and competing orders.