Pressure-induced higher-order topological phase in CsAu3S2

Abstract

External pressure is an efficient means for manipulating various topological states (such as topological insulators and topological semimetals), yet its potential for driving higher-order topology remains relatively unexplored. In this work, we propose that CsAu3S2 provides an ideal system for exploring pressure-driven higher-order topological phases. Based on first-principles calculations and developed tight-binding models, CsAu3S2 is identified as a real Chern insulator with hinge states below 22.5 GPa, while it evolves into a real nodal line semimetal driven by a double band inversion under external pressure exceeding 22.5 GPa. When SOC is included, the system exhibits a rich pressure-induced topological phase diagram. A band inversion occurs at 17.2 GPa, driving a topological phase transition from a real Chern insulator to a topological insulator. A second band inversion at 24.7 GPa further transforms the system into a higher-order topological insulator, characterized by the inversion symmetry-based indicator z4 = 2 and the emergence of six pairs of spin Weyl nodes. The interplay between high pressure and spin–orbit coupling endows CsAu3S2 with a rich variety of topological phases, rendering it a promising candidate for exploring pressure-induced topological phase transitions.