Altermagnets host chirally split magnons that promise unique functionalities for information processing. However, their distinctive transport signatures, crucial for experimental identification and manipulation, remain elusive. Here, we predict that a spin accumulation electrically injects a ``vector" or multidirectional magnon spin current into an altermagnet, comprising both longitudinal and sizable transverse components. Notably, this transverse current exhibits a sign reversal away from the source and can be switched on or off by reorienting the N\'eel vector. While such a transverse current is found to be not forbidden even in conventional antiferromagnets, we demonstrate through quantum-kinetic calculations that in altermagnets, the transverse response is enhanced by two orders of magnitude due to broken parity-time symmetry. This giant enhancement provides a decisive transport fingerprint for detecting magnon spin splitting and N\'eel-vector orientation, offering a clear criterion to experimentally distinguish altermagnets from conventional antiferromagnets.
@article{arxiv.2605.01225,
title = {Vector Magnonics: Electrical Injection and Control of Spin Flow in Altermagnets},
author = {Yanmeng Lei and Rui-Chun Xiao and Weiwei Lin and Tao Yu},
journal= {arXiv preprint arXiv:2605.01225},
year = {2026}
}