Clean 2D superconductivity in a bulk van der Waals superlattice*

Recent interest in bulk van der Waals systems has been driven by the search for exotic physics in thin flakes exfoliated from bulk crystals and, more broadly, the desire to add novel functionalities to those available in the van der Waals heterostructure toolkit. This top down approach has proved successful in unveiling novel phenomena, the MX₂ transition metal dichalcogenides being one such case where both flakes and heterostructures have been used to uncover and design exotic ground states, respectively. However, such devices have intrinsic limitations that can impede powerful experimental probes or prevent the realization of exotic physics in the first place due to disorder introduced through the fabrication process. Here, we report experimental evidence for a possible solution in the form of a bulk single crystal, van der Waals superlattice that simultaneously exhibits high cleanliness and two-dimensional superconductivity.