Superconductivity with Topological non-trivial surface states in NbC

TL;DR

This study demonstrates that NbC is a type-II superconductor with a critical temperature around 8.9K, exhibiting topologically non-trivial surface states, confirmed through DFT calculations and experimental measurements.

Contribution

The paper provides the first detailed analysis combining DFT calculations and experimental data to show NbC's topologically non-trivial surface states alongside its superconductivity.

Findings

NbC exhibits topologically non-trivial band structure.

Bulk superconductivity at 8.9K confirmed experimentally.

NbC is a strong type-II superconductor with a large intermediate state.

Abstract

Quantum materials with non-trivial band topology and bulk superconductivity are considered superior materials to realize topological superconductivity. In this regard, we report detailed Density Functional Theory (DFT) calculations and Z2 invaraints for the NbC superconductor, exhibiting its band structure to be topologically non-trivial. Bulk superconductivity at 8.9K is confirmed through DC magnetization measurements under Field Cooled (FC) and Zero Field Cooled (ZFC) protocols. This superconductivity is found to be of type-II nature as revealed by isothermal M-H measurements and thus calculated the Ginzberg-Landau parameter. A large intermediate state is evident from the phase diagram, showing NbC to be a strong type-II superconductor. Comparing with earlier reports on superconducting NbC, a non-monotonic relationship of critical temperature with lattice parameters is seen. In conclusion, NbC is a type-II around 10K superconductor with topological non-trivial surface states.