In this individual investigator project new high frequency acoustic techniques will be employed to explore the structure of 3He superfluids. The goal is to determine the role of impurities and surface conditions on superfluid 3He and to search for new phases that have been predicted to exist. Such effects are particularly easily controlled in 3He but their existence may be general to other related condensed phases such as the high temperature superconductors. Thus the research may have a significant impact on our society. The stabilization of new superfluid states requires synthesis of aerogels, extremely porous but fairly robust glass solids. Local high school and undergraduate students will be involved in this synthesis. Materials will also be provided collaboratively to laboratories in USA, France, and the United Kingdom for a range of applications. Graduate and undergraduate students will obtain training in technically sophisticated techniques including of small angle x-ray scattering, low-temperature methods, and high frequency acoustics. This will prepare them for a range of professional career opportunities with a significant potential impact to our society.
This individual investigator award supports a project aimed at understanding the new phases and unusual properties of superfluid 3He that have recently been discovered as a consequence of introducing impurities into the superfluid using high porosity silica aerogels. This project aims to address; "What are the stable phases and what determines the transition from one to another?" The effect of correlations between impurities and the possible stabilization of interesting new states of matter by organizing these impurities with externally imposed global anisotropy will also be explored. Heat capacity and high frequency acoustic measurements will be performed at low-temperatures to investigate the superfluid order parameter and phase stability. Additionally, the basic interactions responsible for, and competing with, superfluidity will be measured. New acoustic cavity methods will be developed and applied to explore newly discovered magneto-acoustic effects and to look for stripe phases that have been predicted to form in thin slabs. This research may impact on our understanding of high temperature superconductivity, and thus future technologies. The silica aerogels will be grown and characterized with the involvement of undergraduate and high school students. Characterization will be performed using the small angle X-ray scattering facilities at the Advanced Photon Source, Argonne National Laboratory. Undergraduate and graduate students will obtain training in technically sophisticated techniques, which will prepare them for a range of professional career opportunities with a significant potential impact on our society.
We have shown from acoustic impedance experiments that uniaxially compressed aerogel doesn’t stabilize an axial state of superfluid 3He as was recently speculated. In our experiments with a new NMR set-up we have discovered a textural cross-over transition at low temperatures in superfluid 3He similar to the Frederik’s transition in a nematic liquid crystal. We discovered a new order parameter collective mode near the pair breaking threshold frequency in superfluid 3He. This exotic high angular momentum state is directly analogous to meson excited states. Such a state is classified in high energy physics as a new particle. We measured acoustic attenuation from Andreev bound states at the helium interface. We have used transverse sound to determine f-wave pairing interactions and F2s from the J = 2 imaginary order parameter collective modes (OPCM) and from the acoustic Faraday effect in superfluid 3He. In this project I have trained five graduate students, one postdoctoral fellow, four undergraduate, students, and graduated two PhD’s, both of whom have been selected for tenure line faculty positions at top ranked research Universities. I have served on editorial boards of three professional publications: I am the editor of a continuing Book Series "Progress in Low Temperature Physics" (Elsevier); for seven years I have been the regional editor for North America of the open-access journal, "The New Journal of Physics" (IOP); and I have been on the editorial board of the "Journal of Low Temperature Physics" (Springer). I have served as an expert reviewer for the National Academies of a report on the availability of helium. I have been asked to testify in congress on the availability of a rare isotope of helium. I have been asked to testify on behalf of the Federal Trade Commission. I was the organizer of a conference on Low Temperature Physics "QFS2009: International Symposium on Quantum Fluids and Solids", generally held every two years out of three attended by 250 participants including four Nobel Laureates.
