Superconductivity in the High-Entropy Ceramics Ti 0.2 Zr 0.2 Nb 0.2 Mo 0.2 Ta 0.2 C x with Possible Nontrivial Band Topology.

Topological superconductors have drawn significant interest from the scientific community due to the accompanying Majorana fermions. Here, the discovery of electronic structure and superconductivity (SC) in high-entropy ceramics Ti 0.2 Zr 0.2 Nb 0.2 Mo 0.2 Ta 0.2 C x (x = 1 and 0.8) combined with experiments and first-principles calculations is reported. The Ti 0.2 Zr 0.2 Nb 0.2 Mo 0.2 Ta 0.2 C x high-entropy ceramics show bulk type-II SC with T c ≈ 4.00 K (x = 1) and 2.65 K (x = 0.8), respectively. The specific heat jump (∆C/γT c ) is equal to 1.45 (x = 1) and 1.52 (x = 0.8), close to the expected value of 1.43 for the BCS superconductor in the weak coupling limit. The high-pressure resistance measurements show a robust SC against high physical pressure in Ti 0.2 Zr 0.2 Nb 0.2 Mo 0.2 Ta 0.2 C, with a slight T c variation of 0.3 K within 82.5 GPa. Furthermore, the first-principles calculations indicate that the Dirac-like point exists in the electronic band structures of Ti 0.2 Zr 0.2 Nb 0.2 Mo 0.2 Ta 0.2 C, which is potentially a topological superconductor. The Dirac-like point is mainly contributed by the d orbitals of transition metals M and the p orbitals of C. The high-entropy ceramics provide an excellent platform for the fabrication of novel quantum devices, and the study may spark significant future physics investigations in this intriguing material.