Supercell Altermagnets

TL;DR

This paper introduces supercell altermagnets, expanding the class of altermagnetic materials by considering larger magnetic unit cells with non-zero propagation vectors, enabling control over magnetic order parameter orientation.

Contribution

It predicts and characterizes supercell altermagnets with enlarged magnetic unit cells, broadening the scope of altermagnetic candidates and enabling order parameter control.

Findings

Identified MnSe₂ as a d-wave altermagnet candidate.

Found RbCoBr₃, CsCoCr₃, BaMnO₃ as g-wave candidates.

Demonstrated reorientation of order parameter in MnSe₂ with minimal energy difference.

Abstract

Altermagnets are compensated magnets with unconventional $d$, $g$, and $i$-wave spin order in reciprocal space. So far the search for new altermagnetic candidates has been focused on materials in which the magnetic unit cell is identical to the non-magnetic one, i.e. magnetic structures with zero propagation vector. Here, we substantially broaden the family of altermagnetic candidates by predicting supercell altermagnets. Their magnetic unit cell is constructed by enlarging the nonmagnetic primitive unit cell, resulting in a non-zero propagation vector for the magnetic structure. This connection of the magnetic configuration to the ordering of sublattices gives an extra degree of freedom to supercell altermagnets, which can allow for the control over the order parameter spatial orientation. We identify realistic candidates MnSe$_2$ with a $d$-wave order, and RbCoBr$_3$, CsCoCr$_3$, and BaMnO$_3$ with $g$-wave order. We demonstrate the reorientation of the order parameter in MnSe$_2$, which has two different magnetic configurations, whose energy difference is only 5 meV, opening the possibility of controlling the orientation of the altermagnetic order parameter by external perturbations.