Mixed phases in a Fermi--Hubbard model describing altermagnetism

TL;DR

This paper investigates an extended 2D Fermi--Hubbard model relevant to altermagnetism, revealing a large parameter regime where mixed phases occur, indicating potential for observing exotic physics in cold atom experiments.

Contribution

It introduces an updated Hartree--Fock method to detect phase separation in the model, demonstrating the prevalence of mixed phases at half-filling.

Findings

Large parts of the parameter space exhibit mixed phases.

Mixed phases suggest the presence of exotic physics.

Model parameters are accessible in cold atom experiments.

Abstract

We study an extension of the 2D Fermi--Hubbard model, which was recently introduced in [Das et al., Phys. Rev. Lett. 132, 263402 (2024)] and shown to describe altermagnetism that can be studied in cold atom systems. Using an updated Hartree--Fock method that can detect instabilities towards phase separation, we show that the model is in a mixed phase in large parts of the parameter regime at half-filling. We argue that the occurrence of a mixed phase is an indication of exotic physics which, in this model, occurs in parameter regimes accessible in cold atom experiments.