Pressure-induced superconductivity in the topological crystalline insulator NaCd4As3

This is the authors' abstract. We don't add key points for this paper.

Recently, a united symmetry-protected topological crystalline insulator (TCI) NaCd₄As₃ has been discovered experimentally, which further features a temperature-driven transformation from TCI to TI due to the mirror symmetry broken across a rhombohedral-to-monoclinic structural transition. Here, we report the pressure tuning of structural property and emergence of superconductivity in TCI NaCd₄As₃ by comprehensive high-pressure experiments in diamond-anvil cell. Temperature-dependent Raman measurements show that the structural transition temperature gradually reduces upon compression and is completely suppressed above ~4 GPa. The stable rhombohedral phase further undergoes amorphization evidenced by synchrotron x-ray-diffraction result, which sets in at 20.7 GPa and completes at 34.4 GPa. Along with the complete amorphization, the metallization and superconductivity with a critical temperature Tc~2.5 K appear simultaneously, as observed in transport experiments. We argue that the sudden enhancement in Tc across 60.0 GPa is likely related to the pressure-driven amorphous polymorphism. Our finding unravels the fundamental structure-property relationship and highly tunable crystallographic symmetry in NaCd₄As₃ by external pressure, potentially sparking further investigations via alternative tuning strategies.