Quantum Fluids in One and Two Dimensions

This is a low temperature physics research project. Liquid He-3 and liquid He-4 are paradigm systems that exhibit macroscopic quantum behavior, obeying respectively Fermi and Bose statistics. While a great deal has been learned about these quantum liquids in bulk, fascinating results are still being discovered in atomically thin films of He-3 and He-4 adsorbed on surfaces. Recent measurements found that He-3 atoms tend to float on top of a He-4 film and phase separate into 2-dimensional vapor and liquid phases. Heat capacity measurements are planned to elucidate the nature of this phase separation/transition to determine whether this intrinsically quantum system is also a physical realization of the celebrated 2D Ising model of Onsager. Nuclear magnetic resonance and heat capacity measurements will study the properties of He-3 and He-4 adsorbed in MCM-41, a highly porous substrate with one dimensional pores of 2.5 to 5.0 nm in diameter and up to 500 nm in length. Results of these measurements will be tested against the theories of one dimensional quantum systems. Undergraduate and graduate students involved in these experiments receive rigorous training in cryogenic, high vacuum and ultrasensitive electronic measurements. They must integrate these skills to complete demanding experiments, a process that quickly and elegantly prepares them for careers in government, industry and academe.

This is a low temperature physics project. All substances freeze into solid when the temperature is reduced. The exceptions being liquid He-3 and He-4, which remain liquid even at absolute zero. The reason for this is related to the quantum uncertainty principle. Although chemically identical, He-3 has one neutron and two protons in its nucleus and He-4 has two of each. All atoms are either Fermion or Boson depending on the total number of neutrons, protons and electrons they have. This rule makes He-3 a Fermion and He-4 a Boson, and as a consequence, liquid He-3 and liquid He-4 behave quite differently, particularly when these 'quantum fluids' are forced into volumes where at least one dimension is 'nanoscopic'. This project seeks to understand the properties of one and two-dimensional Fermion and Boson systems, namely He-3 and He-4 atoms confined in atomically thin films, or in tiny one-dimensional pores, with diameters in the range 2.5 to 5.0 nanometers. The knowledge we gain in studying these quantum liquids contributes to the understanding of superconductors and other electronic systems. Undergraduate and graduate students involved in these experiments receive rigorous training in cryogenic, high vacuum and ultrasensitive electronic measurements. They must integrate these skills to complete demanding experiments, a process that quickly and elegantly prepares them for careers in government, industry and academe.