A new strongly topological node-line semimetal β-PbO2

By first-principles calculations, we find that PbO2 is a strongly topological node-line semimetal (NLSM), which is protected by the coexistence of the time-reversal and spatial inversion symmetry when the spin-orbit coupling (SOC) is ignored. In the three dimensions Brillouin zone, there are two node-line rings around the Γ point, perpendicular to each other. It is different to the previously NLSM which has one or three node-line rings in the Brillouin zone. The drumhead-like surface states also can be obtained on both the (100) and (010) surfaces. When the SOC is included, a small gap opened along the nodal line, this material becomes a topological insulator. Therefore, our discovery renders an ideal platform for experimental exploration of the fundamental physics of topological node-line semimetals.