Artificial Cooper-pair Density Modulation in Buckled Heterostructure

Pair density wave (PDW), characterized by the periodic oscillation of pairing order parameters in real space, is a novel quantum phase observed in superconducting (SC) systems¹. It is widely believed to play a crucial role in explaining the nature of the pseudogap phase in superconductors and has recently been discovered in bulk cuprate^{2, 3}, transition-metal dichalcogenide systems^{4, 5}, and other unconventional superconductors^6-8. However, artificial PDW explored in designable two-dimensional materials is rare. In this study, we report a strain-assisted strategy for artificially realizing the Cooper-pair density modulation in a van der Waals heterostructure: graphene on the SC 2H-NbSe₂. Superconductivity is introduced into graphene through the proximity effect. Meanwhile, the graphene membrane spontaneously buckled into a periodic structure due to strain, featuring spatially modulated local density of states (LDOS). The interplay between spatially modulated LDOS and proximity-induced superconductivity results in an oscillatory pair density determined by the buckled geometry, i.e., an artificial PDW. This makes it possible to engineer the PDW with a periodicity up to tens of nanometer scales and realize artificial PDW in various other heterostructures of different designs. Our work provides insight into the study of PDW physics with predesigned two-dimensional materials.