Superfluid response of parahydrogen clusters in superfluid He-4

First principle computer simulations yield evidence of a finite superfluid response at low temperature of a parahydrogen cluster of 15 molecules in bulk superfluid He-4. The superfluid fraction is worth ~44% at T=0.25 K, growing to about 66% at T=0.15 K, i.e., it is substantially reduced compared to that of the same cluster in vacuo, due to higher molecular localization. The implications of these findings on the interpretation of experiments with linear molecules embedded in parahydrogen clusters immersed in superfluid helium are discussed.