Altermagnets host unconventional spin-polarized bands despite zero net magnetization, but controlling their spin structure remains challenging. We propose a multi-field approach to engineer spin polarization in d-wave altermagnets using gating, optical driving, and in-plane electric fields, which enable tunable and switchable polarizations along multiple directions. Optical driving induces out-of-plane (z) polarization, while gating and in-plane fields generate x- and y-polarizations via the Edelstein effect, all of which are experimentally detectable. We further find that spin- and band-selective doping induces chiral optical activity, a feature unique to altermagnets. Our approach provides a versatile route for full control of spin polarization in altermagnets.
@article{arxiv.2510.02452,
title = {Spin polarization engineering in $d$-wave altermagnets},
author = {Mohsen Yarmohammadi and Marco Berritta and Marin Bukov and Libor Šmejkal and Jacob Linder and Peter M. Oppeneer},
journal= {arXiv preprint arXiv:2510.02452},
year = {2026}
}