Revealing the Role of the Tetragonal Distortion in the Metal-Insulator Transition of Co- and Fe-Doped NiS.

Although the NiS exhibits the most widely adjustable metal-to-insulator (MIT) properties among the chalcogenides, the mechanisms, with respect to the regulations in their critical temperatures ( T MIT ), are yet unclear. Herein, we demonstrate the overlooked role associated with the structurally tetragonal distortion in elevating the T MIT of NiS; this is in distinct contrast to the previously expected hybridization and bandwidth regulations that usually reduces T MIT . Compared to the perspective of structure distortions, the orbital hybridization and band regulation of NiS are ∼19 times more effective adjustment in T MIT . As a result, the respective abruptions in both the electrical and thermal resistive switches across the T MIT of NiS can be better preserved in the low-temperature range (<273 K), shedding light on their optimum usage at cryogenic temperatures.