Pair Density Waves and Supercurrent Diode Effect in Altermagnets

TL;DR

This paper demonstrates that metallic altermagnets can host pair density wave states without external magnetic fields, exhibiting non-reciprocal supercurrents and potential supercurrent diode effects, advancing understanding of unconventional superconductivity.

Contribution

It reveals the emergence of pair density wave states in altermagnets driven by momentum-dependent spin splitting, including their supercurrent properties and experimental signatures.

Findings

Identification of pair density wave states in altermagnets.

Discovery of non-reciprocal supercurrents in these states.

Proposal of supercurrent diode effect as an experimental probe.

Abstract

Metallic altermagnets are unusual collinear magnets that feature zero net magnetization with momentum-dependent spin splitting. Here, we show that this spin splitting can induce pair density wave states even in the absence of external magnetic fields. Focusing on BCS-type attractive interactions, we find the stabilization of symmetrically distinct pair density wave states depending on the chemical potential. These states include Fulde-Ferrell and Fulde-Ferrell* states, both of which break inversion symmetry. We investigate the supercurrent properties and discover non-reciprocal supercurrents for both the Fulde-Ferrell and Fulde-Ferrell* states with distinct spatial dependencies. We propose that the supercurrent diode effect can serve as an experimental tool for distinguishing between different pair density waves in metallic altermagnets and discuss the relation to material candidates.