Realization of nodal-ring semimetal in pressurized black phosphorus

Nodal-ring semimetals have attracted attention for their unique band topology and resulting nontrivial quantum phenomena. Using fermiology under high pressure, the authors reveal here a pure nodal-ring semimetal state in pressurized black phosphorus. Semimetallic black phosphorus can provide an ideal platform to explore the true nature of this topological quantum state using external pressure as an effective tuning parameter.