AC conductivity and magnetic dichroism of two-dimensional antiferromagnetic Dirac semimetals

We investigate the magneto-optical properties of two-dimensional nonsymmorphic Dirac semimetals in the presence of antiferromagnetic order. Using the Kubo formula, we calculate the conductivity tensor of two-dimensional CuMnAs, a prototype antiferromagnetic Dirac material, as a function of light frequency. From the finite-frequency conductivity tensor, we derive the dynamic dielectric function and magnetic linear dichroism, demonstrating how they are influenced by the orientation of the N\'eel order parameter. Adjusting the N\'eel vector changes both the sign and amplitude of the system's magneto-optical response. We propose that magnetic linear dichroism spectroscopy is a powerful technique for determining the orientation of the N\'eel vector.