Unconventional ferromagnetism and spin-triplet superconductivity in the imbalanced Kagome-lattice Hubbard model

TL;DR

This study explores how interactions in the kagome-lattice Hubbard model lead to unconventional ferromagnetism and triplet superconductivity, revealing complex quantum states influenced by lattice geometry and electron correlations.

Contribution

It demonstrates the emergence of spin-triplet f-wave superconductivity and distinct ferromagnetic orders driven by electron interactions in the kagome lattice.

Findings

Spin-$z$ ferromagnetism exists and is maximized at moderate interactions.

Transverse $xy$-plane ferromagnetism appears above a critical interaction $U_c/t=3.65$.

The magnetic transition belongs to the 3D XY universality class.

Abstract

Unconventional ferromagnetism and superconductivity in the imbalanced kagome-lattice Hubbard model are investigated by the mean-field theory and determinant quantum Monte Carlo method. Due to the asymmetric band structure of kagome lattice, the spin-$z$ ferromagnetic order intrinsically exists in the system, which is first enhanced by the interaction, and then continuously destructed after reaching a maximum at a moderate interaction strength. In contrast, the $xy$-plane ferromagnetism develops only above a critical interaction, which is estimated to be $U_c/t=3.65 \pm 0.05$ by finite-size scaling. We further verify the nature of the above transverse magnetic transition, and demonstrate it belongs to the three-dimensional $XY$ universality class. Finally, we study the superconducting property, and reveal the possible superconducting state has a triplet $f$-wave pairing symmetry. Our results uncover the exotic quantum states induced by the interactions on kagome lattice, and provide important insights regarding the interplay between electronic correlations and geometry frustrations.