Beyond Conventional Charge Density Wave for Strongly Enhanced 2D Superconductivity in 1H-TaS Superlattices.

Noncentrosymmetric transition metal dichalcogenide (TMD) monolayers offer a fertile platform for exploring unconventional Ising superconductivity (SC) and charge density waves (CDWs). However, the vulnerability of isolated monolayers to structural disorder and environmental oxidation often degrade their electronic coherence. Herein, an alternative approach is reported for fabricating stable and intrinsic monolayers of 1H-TaS sandwiched between SnS blocks in a (SnS)TaS van der Waals (vdW) superlattice. The SnS block layers not only decouple individual 1H-TaS sublayers to endow them with monolayer-like electronic characteristics, but also protect the 1H-TaS layers from electronic degradation. The results reveal the characteristic 3 × 3 CDW order in 1H-TaS sublayers associated with electronic rearrangement in the low-lying sulfur p band, which uncovers a previously undiscovered CDW mechanism rather than the conventional Fermi surface-related framework. Additionally, the (SnS)TaS superlattice exhibits a strongly enhanced Ising-like SC with a layer-independent T of ≈3.0 K, comparable to that of the isolated monolayer 1H-TaS sample, presumably attributed to their monolayer-like characteristics and retained Fermi states. These results provide new insights into the long-debated CDW order and enhanced SC of monolayer 1H-TaS, establishing bulk vdW superlattices as promising platforms for investigating exotic collective quantum phases in the 2D limit.