Chiral-split magnons in the S = 1 Shastry-Sutherland model

TL;DR

This paper investigates the magnon band structure in the S=1 Shastry-Sutherland model, revealing chirality-split bands with opposite splitting directions, leading to robust spin transport effects without external fields.

Contribution

It demonstrates the existence of alternating chirality-split magnon bands in a specific quantum magnetic model, a phenomenon not previously observed in this context.

Findings

Chirality-split magnon bands with opposite splitting directions are identified.

Robust spin Seebeck and spin Nernst effects are predicted without external magnetic fields.

Magnon transport properties are significantly affected by chirality splitting.

Abstract

In ferromagnets, magnons have only one chirality; while in common antiferromagnets, bands with opposite chiralities are degenerate across the Brillouin zone. Recent studies have shown that it is possible to observe non-degenerate bands of opposite chiralities in altermagnetic materials. Here we take the S = 1 Shastry-Sutherland model, which shows the collinear N\'eel (I) phase, and investigate the magnon band structure showing alternate chirality-splitting and the resulting transport properties. In magnon bands, we find a notable feature of the chirality-split magnon bands, and the split is opposite along two different directions in the Brillouin zone. We also calculate the spin and thermal conductivities using Kubo formalism. Our calculations show robust spin Seebeck and spin Nernst effects due to the alternating chirality split across the Brillouin zone, without any external magnetic field and spin-orbit coupling.