The fate of $p$-wave spin polarization in helimagnets with Rashba spin-orbit coupling

TL;DR

This paper investigates how Rashba spin-orbit coupling influences $p$-wave spin polarization in helimagnets, finding that while individual helimagnets are sensitive to spin-orbit effects, coupled antiferromagnetic helimagnets exhibit robust $p$-wave polarization suitable for spintronics.

Contribution

It demonstrates that $p$-wave spin polarization remains robust in antiferromagnetically coupled helimagnets despite Rashba spin-orbit interactions, eliminating the need for fine-tuning.

Findings

$p$-wave symmetry is weakly affected by Rashba interactions unless helix period is very short.

Antiferromagnetically coupled helimagnets exhibit stable $p$-wave spin polarization regardless of periodicity.

Robust $p$-wave magnetism in coupled chains makes them promising for spintronic devices.

Abstract

It has recently been realized that magnetic systems with coplanar magnetic order that are invariant under the combined operation of time-reversal and translation with half a unit cell feature energy bands with a symmetry-protected p-wave spin polarization. Such $p$-wave magnets are a sought-after spin analogy of unconventional triplet superconducting pairing and show promise for use in spintronics. Metallic helimagnets provide a realization of $p$-wave magnetism, but such order often occurs in systems lacking inversion symmetry so that Rashba spin-orbit interactions can be prominent. An important question is therefore how the magnitude and the existence of $p$-wave spin polarization is affected by Rashba spin-orbit interaction. Here, we prove that while the $p$-wave symmetry of the spin-polarized bands is strictly speaking removed by such spin-orbit interactions in helimagnets unless the period of the helix is fine-tuned, the actual quantitative deviation from $p$-wave symmetry is extremely weak unless the period of the helix is only a few lattice sites. Thereafter, we show that the $p$-wave magnetism becomes completely robust in pairs of antiferromagnetically coupled helices. More precisely, the $p$-wave spin-polarization of the bands then appears regardless of the periodicity and regardless of the strength of the spin-orbit interactions. This shows that antiferromagnetically coupled helimagnetic chains produce robust $p$-wave spin polarization free of fine-tuning requirements, making them attractive for potential spintronic applications.