Coupling of magnetism and Dirac fermions in layered topological semimetals*

Dirac semimetals remain at the forefront of research on topological materials because of the fascinating quantum electronic phenomena they exhibit and of their potential technological applications. The family of 112 ternary pnictogens with the general formula A/RMnX2 (A = Ca, Sr; R = Yb, Eu; X = Bi, Sb) have attracted particular attention due to the combination of highly anisotropic Dirac dispersion in quasi-two-dimensional (2D) square nets of X atoms and strongly correlated magnetism of Mn. Both the interlayer charge transport and the magnetic correlations between the Mn layers require that Dirac carriers are coupled to strongly correlated Mn electrons. This work reveals effects of such coupling on antiferromagnetic spin waves of Mn moments and establishes the trend connecting the strength of spin-fermion coupling and the ensuing spin-wave damping with the magnetic interaction parameters and the strength of spin-orbit interaction. These results establish the systematics of spin-fermion interactions in layered magnetic Dirac materials, guiding both theoretical and technological development.