Interlayer Exchange Coupling and Local Superfluidity in (4He)N around C20

The path-integral Monte Carlo method has been employed to study local superfluidity of 4 He layers adsorbed on a C-20 molecular surface. Strong inhomogeneity in the superfluid response between the first two helium layers around the fullerene molecule is found. Furthermore we find that even the strongly-bound first layer exhibiting a clear structural order has a finite superfluid fraction when the second layer is filled with itinerant helium atoms. This first-layer superfluidity is understood to be due to exchange coupling mediated by the second-layer helium atoms.