A new approach to N-doped di-molybdenum carbide with enhanced superconductivity via Urea

TL;DR

This study introduces a simple urea-based method to dope alfa-Mo2C with nitrogen, significantly enhancing its superconducting transition temperature and providing insights into the underlying electron-phonon interactions.

Contribution

The paper presents a novel urea synthesis approach for N-doping in alfa-Mo2C, leading to increased Tc and a broader superconducting dome, with detailed experimental and theoretical analysis.

Findings

Superconducting Tc increased from 2.68 K to 7.05 K with nitrogen doping.

Nitrogen doping causes lattice parameter variation without changing alfa-Mo2C structure.

Enhanced electron-phonon coupling explains the Tc increase.

Abstract

Chemical doping is a critical factor in the development of new superconductors or optimizing the superconducting transition temperature (Tc) of the parent superconducting materials. Herein, a new simple urea approach is developed to synthesize the N-doped alfa-Mo2C. Benefiting from the simple urea method, a broad superconducting dome is found in the Mo2C1-xNx compositions. XRD results show that the structure of alfa-Mo2C remains unchanged and that there is a variation of lattice parameters with nitrogen doping. Resistivity, magnetic susceptibility, and heat capacity measurement results confirm that the superconducting transition temperature (Tc) was strongly increased from 2.68 K (x = 0) to 7.05 K (x = 0.49). First-principles calculations and our analysis indicate that increasing nitrogen doping leads to a rise in the density of states at the Fermi level and doping-induced phonon softening, which enhances electron-phonon coupling. This results in an increase in Tc and a sharp rise in the upper critical field. Our findings provide a promising strategy for fabricating transition metal carbonitrides and provide a material platform for further study of the superconductivity of transition metal carbides.