Molecular superfluidity ?

Bosons could become superfluid at low temperatures: it flows without feeling the friction. This is so due to the opening of an energy gap as bosons condense into a so-called macro-molecule in the presence of interactions. It is expected that such condensation happens at a number of bosons. Now it was demonstrated that, this number can be down to 9 pH2 molecules.

Clusters of para-hydrogen (pH2) have been predicted to exhibit superfluid behavior, but direct observation of this phenomenon has been elusive. Combining experiments and theoretical simulations, we have determined the size evolution of the superfluid response of pH2 clusters doped with carbon dioxide (CO2). Reduction of the effective inertia is observed when the dopant is surrounded by the pH2 solvent. This marks the onset of molecular superfluidity in pH2. The fractional occupation of solvation
rings around CO2 correlates with enhanced superfluid response for certain cluster sizes. [PRL 105, 133401 (2010)]