Elevating the Superconducting Temperature in Epitaxially Stabilized Rock-Salt NbO

Niobium monoxide generally refers to Nb3O3 with a pseudorock-salt structure, which is known as thermodynamically the most stable phase, exhibiting superconductivity below 1.38 K; neither bulk nor thin film form of rock-salt NbO thus has been reported so far. In this study, metastable rock-salt NbO has been successfully synthesized through a nonequilibrium process with vapor deposition. The present synthesis of rock-salt NbO marked its enhancement of superconductivity, whose transition temperature could reach up to 7.4 K, more than 5 times as high as that of the pseudorock-salt Nb3O3. The structure-sensitive electronic properties of the rock-salt NbO will be further discussed not only experimentally but also theoretically with the aid of DFT + U + V calculations.