Effects of Mo Doping on the Superconducting Properties of NbSe ₂

Transition metal dichalcogenides (TMDs) exhibit remarkable tunability in their structural and electronic properties, making them an excellent platform for exploring quantum phases in two-dimensional materials. Among these, 2 H -NbSe 2 is a classic TMD superconductor that shows conventional superconductivity with a relatively high superconducting transition temperature ( T c ) of 7.2 K. In this study, we investigate the effect of Mo doping at the Nb site in NbSe 2, creating the alloy system Nb 1– x Mo x Se 2 (0 ≤ x ≤ 0.15). Notably, a slight increase in T c is observed at a low doping level of x = 0.01, followed by a gradual decrease as Mo content increases, indicating a nonmonotonic relationship between superconductivity and Mo doping. We also found that the critical current density J c increased by approximately 26% for x = 0.01 compared to undoped NbSe 2 . The upper critical field ( B c2 ) is estimated to be approximately 14.71 T for the x = 0.01 sample, which is among the highest reported values for polycrystalline NbSe 2, indicating a significant enhancement in the robustness of the superconducting state of NbSe 2 at low Mo doping levels.