Altermagnetic magnon transport in the \textit{d}-wave altermagnet \ch{LuFeO3}

TL;DR

This paper demonstrates non-local magnon transport in the extit{d}-wave altermagnet extit{LuFeO3}, revealing anisotropic, direction-dependent spin Seebeck effects and sign reversals, supported by simulations and theoretical calculations.

Contribution

First experimental observation of non-local magnon transport in a extit{d}-wave altermagnet, showing anisotropic spin Seebeck effects and symmetry-dependent behavior.

Findings

Non-local spin signals observed at zero magnetic field along specific directions.

Sign reversal of spin Seebeck response between two altermagnetic directions.

Transport effects vanish when aligned with or perpendicular to the easy axis.

Abstract

Altermagnets exhibit a spin-split band structure despite having zero net magnetization, leading to special magnonic properties such as anisotropic magnon lifetimes and field-free spin transport. Here, we present a direct experimental demonstration of non-local magnon transport in the \textit{d}-wave altermagnet \ch{LuFeO3}, using both spin Seebeck and spin Hall effect-based injection and detection. We observe a non-local spin signal at zero magnetic field when the transport is along an altermagnetic direction, but not for transport along other directions. The observed sign reversal between two distinct altermagnetic directions in the spin Seebeck response demonstrates the altermagnetic nature of the magnon transport. In contrast, when transport is aligned along or perpendicular to the easy axis, both the first-harmonic signal and the sign-reversal effect vanish, consistent with symmetry-imposed suppression. These findings are supported by atomistic spin dynamics simulations, as well as linear spin wave theory calculations, which explain how our altermagnetic system hosts anisotropic spin Seebeck transport. Our results provide direct evidence of direction-dependent magnon splitting in altermagnets and highlight their potential for field-free magnonic spin transport, offering a promising pathway for low-power spintronic applications.