Chapter 5 Two-Dimensional Physics

Abstract

This chapter discusses various examples of systems that can more or less be regarded as two-dimensional. Monolayers of gas adsorbed onto some substrate provide obvious examples. It is important that the substrate should have a surface that is clean and homogeneous, and helpful if it has a large surface to volume ratio. Various sorts of finely divided powders, "Vycor", which is a porous glass, and "grafoil," which is graphite expanded so that there are only a hundred or so atomic layers between each surface are all suitable substrates. Monolayers of inert gases such as helium, neon, and argon can display solid, liquid, and gas phases, with properties somewhat different from the bulk materials. With helium, if the coverage is greater than a single monolayer, superfluidity can occur at low temperatures and films of 3He show the effect of Fermi statistics and the nuclear moments give rise to important magnetic effects.