Altermagnetism in modified Lieb lattice Hubbard model

TL;DR

This paper investigates altermagnetism in a modified Lieb lattice Hubbard model, revealing spin-split Mott insulating and metallic phases with unique magnetic and electronic properties.

Contribution

It demonstrates the emergence of altermagnetism in the Lieb lattice Hubbard model through comprehensive theoretical analysis, including Hartree-Fock and exact diagonalization methods.

Findings

Identification of spin-1/2 altermagnetic Mott insulators at specific electron densities.

Evidence of altermagnetic metal with d-wave spin splitting and quasi-1D Fermi surfaces.

Characterization of spin and magnon band splitting in the studied phases.

Abstract

We study the emergence of altermagnetism from repulsive interactions for electrons on the Lieb lattice as a model of quasi-2D oxychalcogenides with the so-called "anti-CuO$_{2}$" lattice structure. A comprehensive study of the Lieb lattice Hubbard model, using unrestricted Hartree-Fock and exact diagonalization techniques, establishes the presence of spin-${1\over 2}$ altermagnetic Mott insulating ground state for average electron densities of 2 and 4 per unit cell. Both phases show the characteristic spin splitting in the electron bands as well as in the magnon bands, as indicated by solutions of an effective spin-${1\over 2}$ Heisenberg model that we construct. We also provide evidence for altermagnetic metal formation in the electron- and hole-doped Mott state, giving rise to Fermi surfaces with $d_{x^{2}-y^{2}}$-wave spin splitting and quasi-one-dimensional characteristics.