Multipolar multiferroics in $4d^2$/$5d^2$ Mott insulators

TL;DR

This paper extends multiferroic concepts to include multipolar orders in $4d^2$/$5d^2$ Mott insulators, showing how complex magnetic multipolar interactions can induce ferroelectricity and new functional properties.

Contribution

It introduces a framework for understanding multipolar multiferroicity in strongly correlated $4d^2$/$5d^2$ systems, highlighting the role of higher-order multipoles.

Findings

Magnetic multipolar interactions originate from strong spin-orbit and Hund's couplings.

Quadrupolar and octupolar orders can induce electrical quadrupolar moments.

Coexistence of multipolar orders suggests new functional properties in correlated materials.

Abstract

We extend the concept of conventional multiferroicity \ -- where ferroelectric and ferromagnetic orders coexist \ -- to include multipolar degrees of freedom. Specifically, we explore how this phenomenon emerges in $4d^2/5d^2$ Mott insulators with strong spin-orbit and Hund's couplings. Our study uncovers the origin of magnetic multipolar interactions in these systems and demonstrates that a combination of quadrupolar and octupolar magnetic order can simultaneously induce both electrical quadrupolar moments and ferroelectric polarization. By expanding the multiferroic framework to higher-order multipoles, we reveal the possibility of coexisting multipolar orders of different or same ranks, paving the way for new functional properties in a large class of strongly correlated materials.