Phonon-enhanced optical spin-conductivity and spin-splitter effect in altermagnets

Abstract: Collinear antiferromagnets with nonrelativistic spin-split bands and no net magnetization, called altermagnets, show interesting transport properties due to their unique band structure. We here compute the linear response optical conductivity of thin films of such materials in the presence of phonon scatterings. Using a tight-binding lattice model for altermagnets and the Holstein model for the phonon sector, we find that the electron-phonon scatterings can strongly increase the spin conductivity at finite frequencies. This occurs despite the fact that the self-energy describing the electron-phonon interactions is spin-independent. Interestingly, we show that electron-phonon scattering also enhances the spin-splitter effect at finite frequencies. These results suggest that altermagnets with strong electron-phonon coupling are favorable with regard to AC spin-polarized transport.