A Simple Urea Approach to N-Doped α-Mo2C with Enhanced Superconductivity

Chemical doping is a critical factor in the development of new superconductors or optimizing the superconducting transition temperature (T-c) of the parent superconducting materials. Here, a new simple urea approach is developed to synthesize the N-doped cx-Mo2C. Benefiting from the simple urea method, a broad superconducting dome is found in the Mo2C1-xNx(0 <= x <= 0.49) compositions. X-ray diffraction results show that the structure of cx-Mo2C remains unchanged and there is a variation of lattice parameters with nitrogen doping. Resistivity, magnetic susceptibility, and heat capacity measurement results confirm that T-c 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 T-c 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.