Superfluid behavior of quasi-one-dimensional p-H_2 inside a carbon nanotube

摘要

We perform ab initio quantum Monte Carlo simulations of para-hydrogen (p-H_2) at T = 0 K confined in carbon nanotubes (CNT) of different radii. The radial density profiles show a strong layering of the p-H_2 molecules which grow, with increasing number of molecules, in solid concentric cylindrical shells and eventually a central column. The central column can be considered an effective one-dimensional (ID) fluid whose properties are well captured by the Tomonaga-Luttinger liquid theory. The Luttinger parameter is explicitly computed and interestingly it shows a nonmonotonic behavior with the linear density similar to what found for pure 1D ~3He. Remarkably, for the central column in a (10,10) CNT, we found an ample linear density range in which the Luttinger liquid is (ⅰ) superfluid and (ⅱ) stable against a weak disordered external potential, as the one expected inside realistic pores. This superfluid behavior could be experimentally revealed in bundles of carbon nanotubes, where deviations from classical inertial values associated with superfluid density could be measured by using quartz crystal microbalance techniques. In summary, our results suggest that p-H_2 within carbon nanotubes could be a practical and stable realization of the long sought-after, elusive superfluid phase of parahydrogen.