Intercalation-Induced Monolayer Behavior in Bulk NbSe₂

Superconductivity at the 2D limit is significant for advancing fundamental physics, leading to extensive research on monolayer two-dimensional materials. In particular, monolayer transition metal dichalcogenides such as NbSe 2 exhibit Ising superconductivity due to broken in-plane inversion symmetry and strong spin–orbit coupling, which has garnered significant attention. In this letter, we adopted an organic cation intercalation technique to modulate the interlayer interaction of NbSe 2 by expanding the interlayer distance, thereby making intercalated NbSe 2 behave similarly to monolayer NbSe 2 . The interlayer distances of NbSe 2 intercalated with THA +, CTA +, and TDA + cations are almost double or triple that of pristine NbSe 2 . The superconducting transition temperature ( T c ) of THA-NbSe 2 is comparable to that of pristine NbSe 2, while the charge density wave (CDW) transition temperature is higher. The T c of intercalated NbSe 2 decreases with a reduced hole concentration, and the enhanced CDW is ascribed to the dimensional reduction. Notably, the in-plane upper critical field of intercalated NbSe 2 significantly exceeds the Pauli paramagnetic limit, which is similar to the Ising superconductivity observed in monolayer NbSe 2 . Our work demonstrates that the organic cations intercalated two-dimensional materials exhibit behavior similar to their monolayer counterparts, providing a convenient platform for exploring and modulating physical phenomena at the two-dimensional limit.