Spin polarization engineering in $d$-wave altermagnets

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.

💡 Research Summary

The authors present a comprehensive scheme for full vector control of spin polarization in two‑dimensional d‑wave altermagnets by combining three external fields: electrostatic gating, circularly polarized light (CPL), and in‑plane electric fields. Starting from a minimal Rashba‑type Hamiltonian that captures the d‑wave altermagnetic exchange term (parameter D) and a conventional kinetic term, they introduce top and bottom gate voltages ±V which generate a Rashba spin‑orbit coupling (SOC) strength λ. A time‑periodic vector potential describing right‑handed CPL, A(t)=Ad