Pieter Gunnink
I will discuss two responses in d-wave altermagnets, which are enabled by their uniquely spin-split band structure: (1) spin demons and a (2) surface acoustic wave driven acoustic spin splitter. First, I will discuss demons, which are a type of plasmons, consisting of out-of-phase oscillations of electrons in different bands [1,2]. I will show that d-wave altermagnets, a recently discovered class of collinear magnetism, naturally realize a spin demon, which consists of out-of-phase movement of the two spin species [3].
Secondly, I will show that surface acoustic waves (SAWs) can generate spin currents in d-wave altermagnets, realizing an acoustic spin splitter [4]. In metallic altermagnets, the electrons form the main response to SAWs, but in insulators the SAW can couple effectively to the magnons. I argue that this provides a novel way to detect the spin splitter effect in insulating altermagnetic thin films.
[1] Pines, Canadian Journal of Physics 34, 1379 (1956).
[2] Husain et al, Nature 621, 66 (2023).
[3] Gunnink, Sinova and Mook, Phys. Rev. Lett. 135, 126701 (2025)
[4] Gunnink, Sinova and Mook, arXiv:2502.18007 (2025)