Ambient-Pressure Superconductivity Onset at 10 K and Robust T under High Pressure in TiNbTaN Medium-Entropy Nitride.

Superconductivity has been one of the focal points in medium- and high-entropy alloys (MEAs-HEAs) since the first discovery of the HEA superconductor in 2014. Until now, most HEAs' superconducting transition temperature (T) has not exceeded 10 K. Here, the first observation of superconductivity in a bulk medium-entropy nitride (MEN), TiNbTaN, which shows a T of 10 K at ambient pressure, is reported. Notably, the electronic specific heat coefficient γ(H) exhibits nonlinear H-dependence behavior, which is similar to other well-studied multigap superconductors. Furthermore, TiNbTaN₃ exhibits extraordinary pressure resilience, maintaining robust superconductivity under high-pressure conditions. Density functional theory (DFT) calculations indicate that pressure exerts a negligible impact on the electronic structures of TiNbTaN, thereby corroborating the experimental observations. These findings not only advance the understanding of emergent phenomena in entropy-stabilized nitrides but also establish a new material platform for finding more high-T superconductors with combinations of 4d/5d transition metal elements and light elements, motivating further investigations into high-entropy functional ceramics for extreme environment applications.