  We studied by means of computer simulations the low temperature properties of
two-dimensional parahydrogen clusters comprising between 7 and 30 molecules.
Computed energetics is in quantitative agreement with that reported in the only
previous study [Phys. Rev. B 65, 174527 (2002)], but a generally stronger
superfluid response is obtained here for clusters with more than ten molecules.
Moreover, all the clusters, including the smallest one, display a well-defined,
clearly identifiable solidlike structure; with only one possible exception,
those with fewer than 25 molecules are (almost) entirely superfluid at the
lowest temperature considered here (i.e., 0.25 K), and can thus be regarded as
nanoscale "supersolids". The implications of these results on a possible bulk
two-dimensional superfluid phase of parahydrogen are discussed.
