"Dirac fermions in an antiferromagnetic semimetal"

Abstract:

Analogues of the elementary particles have been extensively searched for in condensed-matter systems for both scientific interest and technological applications^1, 2, 3. Recently, massless Dirac fermions were found to emerge as low-energy excitations in materials now known as Dirac semimetals^4, 5, 6. All of the currently known Dirac semimetals are non-magnetic with both time-reversal symmetry  and inversion symmetry    ^7, 8, 9. Here we show that Dirac fermions can exist in one type of antiferromagnetic system, where both  and  are broken but their combination is respected. We propose orthorhombic antiferromagnet CuMnAs as a candidate, analyse the robustness of the Dirac points under symmetry protections and demonstrate its distinctive bulk dispersions, as well as the corresponding surface states, by ab initio calculations. Our results provide a possible platform to study the interplay of Dirac fermion physics and magnetism.