Observation of Surface States in Concentric Nodal Line Semimetal Candidate ZrP2*

Topological semimetals have enhanced our understanding of topological states in condensed matter physics. In topological nodal line semimetals, conduction and valence bands cross each other along a closed curve in the three-dimensional Brillouin zone, where no perturbation can remove this crossing line and open a full direct gap between the two bands. These nodal lines are topologically protected by the symmetry group and can be associated with a topological invariant. Here, we present a systematic angle-resolved photoemission spectroscopy study of a topological nodal-line semi metallic state in the transition metal dipnictide ZrP2. Our study reveals the detailed electronic structure of ZrP2, which is protected by non symmorphic symmetry, more specifically the glide symmetry. Our findings reveal that that ZrP2 contains concentric intersecting coplanar ellipse (CICE) nodal lines.