Dirac Charge in Antiferromagnetic Topological Semimetals

Topological node of electronic bands can carry emergent charge degree of freedom such as the Berry curvature monopole of the Weyl semimetals, which results in intriguing transport and optical phenomena. In this Letter, we discuss the existence of the hidden "Dirac charge" and its detection via the photocurrent response in antiferromagnetic (AFM) Dirac semimetals. In light of the Berry curvature defined in the spin and spin-charge-mixed parameter space, we identify Dirac charges as sources or sinks of the Berry curvature in the generalized parameter space. We demonstrate that this Dirac charge can be detected via the photocurrent driven by the spin-charge-coupled motive force. By using real-time simulation, we find that the Dirac charge plays a significant role in the photocurrent generation in AFM Dirac semimetals. This Letter reveals the hidden property of the Dirac points in AFM Dirac semimetals.