Persistent spin textures with collinear spin polarization are promising platforms for spintronics applications. However, their typically relativistic spin-orbit origin leads to weak spin splittings and fragile spin coherence. Here, we demonstrate a previously overlooked class of robust collinear spin polarization protected by mirror symmetry in combination with a strong exchange-driven altermagnetic order, which persists even in the presence of spin-orbit coupling. By combining first-principles calculations with a systematic classification of spin and magnetic layer groups, we identify this phenomenon-termed persistent altermagnetic spin polarization (PASP)-to occur in 158 spin layer groups and in representative materials including metallic V2Te2O, insulating La2CuO4, and semiconducting VSI2. Furthermore, we theoretically demonstrate that PASP is ferroelectrically switchable in VSI2. Finally, we show that this PASP switching can lead to large changes in spin-filtering conductance in a model all-altermagnetic junction. Our results open the possibility of employing PASP in all-altermagnetic magnetic memory and spin-transistor devices and establish universal principles of altermagnetism in spin-orbit-coupled monolayers.
@article{arxiv.2603.12223,
title = {Persistent altermagnetism},
author = {Warlley H. Campos and F. C. Fobasso Mbognou and Anna Birk Hellenes and Joseph Poata and Taikang Chen and Jan Priessnitz and Libor Šmejkal},
journal= {arXiv preprint arXiv:2603.12223},
year = {2026}
}