Helium films from two to three dimensions

Recent studies of helium films adsorbed on uniform solid surfaces reveal a rich variety of distinctive regimes. Monolayer films display several phases approximating two dimensional gases, liquids and solids as well as substrate ordered structures. Detailed theoretical models are achieving considerable quantitative success in describing and predicting properties of most of the phases. An important subset of the current studies involves the evolution from two dimensional to bulk behavior, including the onset of superfluidity.