Mutual enhancement of altermagnetism and ferroelectricity

TL;DR

This paper theoretically investigates the coexistence and mutual influence of ferroelectricity and metallic altermagnetism, revealing how doping levels affect their interplay and proposing electrical tuning methods for magnetic phases.

Contribution

It introduces a self-consistent mean-field Hubbard model analysis showing conditions for coexisting ferroelectricity and altermagnetism, including their mutual enhancement and electrical control.

Findings

Coexistence depends on doping level, with robustness away from half-filling.

Near half-filling, altermagnetism suppresses ferroelectricity.

Electrical tuning can switch altermagnetic phases between nodal and nodeless.

Abstract

We consider theoretically the possibility of coexisting ferroelectric and metallic altermagnetic order, which has recently been predicted in insulating and semiconducting systems via ab initio calculations. Solving self-consistently a mean-field Hubbard model, accounting also for the energy cost of distorting the lattice to produce an electric polarization, our results show that metallic altermagnetism and ferroelectricity suppress or enhance each other depending on the doping level of the system. Close to half-filling, the system can lower its energy by becoming altermagnetic, but at the expense of losing the electric polarization. Away from half-filling, the coexistence of ferroelectricity and altermagnetism is much more robust toward an increase in the energy cost associated with the deformation of the lattice. Therefore, our results suggest that filling fractions corresponding to doping relatively far away from half-filling constitute the most promising regime to look for coexistent ferroelectricity and metallic altermagnetism with mutual enhancement. Moreover, we propose a way to electrically tune altermagnetism between nodal and nodeless phases as well as achieving coexistence of a nodal and nodeless phase for the two spin species.