Altermagnets feature antiparallel spin sublattices with d-, g-, or i-wave spin order, yielding nonrelativistic spin splitting without net magnetization. We show that embedding a two-dimensional d-wave altermagnet in a driven optical cavity induces a finite, tunable magnetization. Coherent photon driving couples selectively to electronic sublattices, and the resulting altermagnets' symmetry-broken spin texture yields a pronounced steady-state spin imbalance -- coherent magnetization -- absent in conventional antiferromagnets for the same lattice configuration. A mean-field Lindblad analysis reveals the dominance of quadratic over linear couplings. In the strong-coupling regime, distinct polariton signatures emerge in the steady state of induced magnetization. This work demonstrates cavity control of altermagnets for spintronic applications.
@article{arxiv.2510.16248,
title = {Cavity-induced coherent magnetization and polaritons in altermagnets},
author = {Mohsen Yarmohammadi and Libor Šmejkal and James K. Freericks},
journal= {arXiv preprint arXiv:2510.16248},
year = {2026}
}