Topological phononic nodal hexahedron net and nodal links in the high-pressure phase of the semiconductor CuCl

Abstract

By using symmetry analysis and first-principles calculations, we propose that the simple cubic structure of copper chloride (CuCl) in high-pressure phase can be worked as a three-dimensional (3D) topological phononic material, hosting the so-called topological phononic nodal links (TPNLs) in phonon spectra, which are intersected around the center of the Brillouin zone (BZ). More interestingly, another class of nodal-line phonons, i.e., the topological phononic nodal hexahedron net (TPNHN), exists at all the boundaries of 3D BZ and is composed of interconnected quadruply degenerate straight nodal lines. Their topologically nontrivial natures are confirmed by the Berry phase calculations. The TPNHN-induced Dirac cones and the TPNLs-induced drumheadlike surface states are observed in the surface BZ. In addition, the appearance of large surface arcs strongly supports the robustness of nodal-link phonons. Our theoretical results not only pave a route to explore new nodal-line phonons but also reveal that the semiconductor CuCl in high-pressure phase is an ideal material candidate to realize TPNHN and TPNLs.