Dimensional crossover in quantum fluids

In one spatial dimension it is not possible to break a continuous symmetry due to strong fluctuations, even at zero temperature. Although fermionic examples of quasi-one-dimensional systems abound, including carbon nanotubes and quantum wires, it is much more difficult to reach this limit in high density bosonic fluids due to a short coherence length on the atomic scale. Recent advances in nanofabrication techniques now allow for the confinement of helium-4 inside pores with nanometer radius, but unequivocal experimental evidence of one-dimensional behavior is still lacking. We have performed large scale quantum Monte Carlo simulations near the superfluid transition and have investigated how the signatures of dimensional crossover are reflected in the thermodynamic properties of nano-confined helium-4. The results hint at the emergence of quantum hydrodynamics inside the pore at length scales that can be probed in the laboratory.