Fig. 2. Crystal symmetry breaking, large spin-split Fermi surface, and Berry curvature in collinear antiferromagnet RuO₂.

(A) Collinear antiferromagnet with effective time-reversal symmetry $\mathrm{T}{\mathbf{t}}_{\frac{1}{2}}$. (B) Left: The unit cell of antiferromagnetic RuO₂ with the Néel vector along the [100] axis and marked crystal symmetries. Right: Detail of the generation of the local crystal chirality by noncentrosymmetric oxygen atoms ${\mathbf{\chi }}_{\mathrm{AB}}^{(C)}\sim {\mathbf{d}}_{\mathrm{AO}}\times {\mathbf{d}}_{\mathrm{OB}}$. (C) Antiferromagnetic Fermi surface cut at wave vector k_z = 0 calculated without spin-orbit coupling. The spin up and down projections are colored in red and blue. (D) Calculations with spin-orbit coupling of crystal momentum resolved Berry curvature Ω_y(k_x, k_y,0) in atomic units.