Third-order charge transport in a magnetic topological semimetal

Abstract

Magnetic topological materials and their physical signatures are a focus of current research. By first-principles calculations and symmetry analysis, we reveal exotic topological semimetal states in an existing antiferromagnet $\mathrm{Th}\mathrm{Mn}{}_{2}{\mathrm{Si}}_{2}$. Depending on the N\'eel vector orientation, the topological band crossings near the Fermi level form either a double-nodal loop or two pairs of Dirac points, which are all fourfold degenerate and robust under spin-orbit coupling. These topological features produce large Berry connection polarizability, leading to pronounced nonlinear transport effects. Particularly, we evaluate the third-order current response, which dominates the transverse current in $\mathrm{Th}\mathrm{Mn}{}_{2}{\mathrm{Si}}_{2}$. We show that the third-order response can be much more sensitive to topological phase transitions than a linear response, which offers a powerful tool for characterizing topological states of matter.