Double-layer electronic systems enable the investigation of interlayer quasiparticle interactions and the discovery of intriguing interlayer correlated states. Here we report interlayer drag measurements between graphene and superconducting LaAlO3/SrTiO3 (LAO/STO) heterointerface separated by a natural insulating barrier of LAO (as thin as 2 nm). Applying a drive current (Idrive) in the graphene layer induces a negative drag voltage at the LAO/STO interface in the vicinity of the superconducting transition, which is attributed to the supercurrent drag effect, arising from the interlayer interactions involving the superconducting carriers. Benefiting from the high tunability of both layers and the ultra-small interlayer spacing, an extremely large interlayer current coupling ratio (r = |Idrag/Idrive|, Idrag: the equivalent drag current at LAO/STO interface) is eventually achieved, surpassing conventional systems consisting of normal metal and superconducting films by two orders of magnitude. More strikingly, this ratio is estimated to be up to 10^5 at the zero-temperature limit. The unique temperature- and carrier density/polarity-dependent behaviors suggest a brand-new microscopic interaction mechanism accounting for the observed giant supercurrent drag effect. Our study is anticipated to inspire further exploration of hybrid interlayer coupling via utilization of newly-emerging two-dimensional electronic systems, in particular those exhibiting long-range electronic and magnetic orders.
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