Abstract
Due to its simple strusture and large zero point motion, helium remains a liquid down to absolute zero, and thus constitutes a quantum fluid. At low temperature, the two stable isotopes of helium exhibit different quantum mechanical behavor due to the fact that 3He is a Fermion and 4He is a Boson. At millikelvin temperatures, 3He acts as an ideal Fermi gas, and 4He exhibits the exotic qualities of a superfluid (no viscosity). In addition to using bulk mixtures of the helium isotopes to achieve temperatures as low as 0.001 K, we study the properties of mixture films. Using the superfluid 4He as a vehicle, we study thin films of 3He which act as ideal two-dimensional gases. We are provided with a simple and beautiful system for the study of our understanding of how atoms interact with one another and the world around them.
The only other systems in which 2D ideal gases are realized are electrons in thin metal films. The study of the metal-insulator transition (MIT) is an important topic in that field, and we can create an analogy of that system in our thin films (3He atoms instead of electrons) in order to try to understand the MIT, simplified by the fact that the 3He atoms do not interact through the Coulomb interaction.