Superconducting phenomena in systems with unconventional magnets

TL;DR

This review discusses recent advances in superconducting phenomena in junctions with unconventional magnets, highlighting their unique properties and potential for quantum applications, a relatively new area of research compared to conventional magnetism.

Contribution

It provides a comprehensive overview of the interplay between superconductivity and unconventional magnets, emphasizing recent progress and fundamental phenomena.

Findings

Unconventional magnets exhibit zero net magnetization and nonrelativistic spin splitting.

Magnetic order can be even or odd with respect to momentum, e.g., $d$-wave and $p$-wave altermagnets.

The interplay between unconventional magnets and superconductivity is a growing research area with potential quantum applications.

Abstract

In this work we review the recent advances on superconducting phenomena in junctions formed by superconductors and unconventional magnets. Conventional magnets, such as ferromagnets and antiferromagnets, are characterized by broken time-reversal symmetry but only ferromagnets produce a finite net magnetization due to parallel spin alignment and spin-split bands in momentum. Very recently, a new type of magnets has been reported and here we refer to them as unconventional magnets because they exhibit special properties of both ferromagnets and antiferromagnets: they exhibit zero net magnetization (like antiferromagnets) and a nonrelativistic spin splitting of energy bands (like ferromagnets), both leading to anisotropic spin-polarized Fermi surfaces. An interesting property of unconventional magnets is that their magnetic order can be even or odd with respect to momentum, where $d$-wave altermagnets and $p$-wave magnets are the most representative examples. In this regard, $d$-wave altermagnets and $p$-wave magnets are seen as counterparts in magnetism of the unconventional $d$- and $p$-wave superconducting states, respectively. While the impact of conventional magnetism on superconductivity has been largely studied, the combination of unconventional magnets and superconductivity has only lately attracted considerably attention. This work provides a comprehensive review of the recent progress on the interplay between superconductivity and unconventional magnets. In particular, we focus on the fundamental emerging superconducting phenomena and also discuss the potential implications towards quantum applications.