Density functional approach to helium at finite temperature

We report an application of the general formalism of density functional theory (DFT) for quantum fluids at finite temperature to the case of helium. Using this approach, we compute the liquid-vapour coexistence curve and the surface tension of helium at low temperatures. We observe that the range of the interface is much larger than the usual 10-90 surface thickness, and we find that the DFT reproduces the T ^{7 / 3} temperature dependence of the surface tension. This implies that capillary-wave effects are, at least partially, accounted for by the density functional.