Topological nodal line semimetals

Fang Chen^{1, †,}, Weng Hongming^{1, 2, ‡,}, Dai Xi^{1, 2}, Fang Zhong^{1, 2}

Manifolds of different dimensions (S⁰, S¹, and S²) that enclose a nodal line. (a) Two points (S⁰) inside and outside the nodal line pinned to (protected by) a mirror plane; (b) a loop (S¹) that threads the nodal line; and (c) a sphere (S²) surrounding the entire nodal line.^[28]