  Topological antiferromagnetic systems, which exhibit anisotropic band
structures combined with complex relativistic spin structures in momentum
space, have shown strong magnetoresistance effects driven by Dirac fermion
characteristics. While these new antiferromagnets have been studied in
transport experiments, very little is known about their spin-dependent
electronic dynamics on ultrafast timescales and far-from-equilibrium behavior.
This paper investigates theoretically the spin-dependent electronic dynamics
due to electron-phonon scattering in a model electronic band structure that
corresponds to a Dirac semimetal antiferromagnet. Following a spin conserving
instantaneous excitation we obtain a change of the antiferromagnetic spin
polarization due to the scattering dynamics for the site-resolved spin
expectation values. This allows us to identify fingerprints of the anisotropic
band structure in the carrier dynamics on ultrashort timescales which should be
observable in present experimental set-ups.
