Emerging research landscape of altermagnetism

TL;DR

This paper discusses altermagnetism, a newly identified magnetic phase that exhibits ferromagnetic-like spin splitting without net magnetization, expanding the understanding of magnetic phenomena in condensed matter physics.

Contribution

It introduces altermagnetism as a third fundamental magnetic phase, supported by a novel symmetry-group formalism, and explores its phenomenology and potential material candidates.

Findings

Identification of altermagnetism as a distinct magnetic phase

Explanation of spin-split spectra with zero net magnetization

Potential impact on condensed-matter physics research areas

Abstract

Magnetism is one of the largest, most fundamental, and technologically most relevant fields of condensed-matter physics. Traditionally, two basic magnetic phases have been considered -- ferromagnetism and antiferromagnetism. The breaking of the time-reversal symmetry and spin splitting of the electronic states by the magnetization in ferromagnets underpins a range of macroscopic responses in this extensively explored and exploited type of magnets. By comparison, antiferromagnets have vanishing net magnetization. This Perspective reflects on recent observations of materials hosting an intriguing ferromagnetic-antiferromagnetic dichotomy, in which spin-split spectra and macroscopic observables, akin to ferromagnets, are accompanied by antiparallel magnetic order with vanishing magnetization, typical of antiferromagnets. An unconventional non-relativistic symmetry-group formalism offers a resolution of this apparent contradiction by delimiting a third basic magnetic phase, dubbed altermagnetism. Our Perspective starts with an overview of the still emerging unique phenomenology of the phase, and of the wide array of altermagnetic material candidates. In the main part of the article, we illustrate how altermagnetism can enrich our understanding of overarching condensed-matter physics concepts, and have impact on prominent condensed-matter research areas.