Artificial Cooper-Pair Density Modulation in Buckled Heterostructure

The pair density wave (PDW), characterized by a periodic real-space modulation of the superconducting pairing order parameter, is a novel quantum phase observed in superconducting (SC) systems. It is believed to play a key role in understanding the pseudogap phase of superconductors and has recently been discovered in bulk cuprates, transition-metal dichalcogenide, and other unconventional superconductors. However, artificially engineered PDW in designable two-dimensional materials remain rare. In this paper, we report a strain-assisted strategy to realize cooper-pair density modulation in a van der Waals heterostructure: graphene on SC 2H-NbSe_2. Superconductivity is induced in graphene via the proximity effect. Meanwhile, the graphene membrane spontaneously buckles into a periodic structure owing to strain, featuring a spatially modulated local density of states (LDOS). The interplay between the spatially modulated LDOS and the proximity-induced superconductivity results in an oscillatory pair density determined by the buckled geometry, constituting an artificial PDW. This approach enables the engineering of PDWs with periodicities of up to tens of nanometers and allows their realization in a variety of heterostructures with tailored designs. Our work provides new insights into the investigation of PDW physics using predesigned two-dimensional materials.