Experiments on Superfluid 3He in Bulk and in Aerogel

Cornell University, Ithaca NY

Investigators

Abstract

This research is focused on the investigation of the properties of superfluid 3He in Aerogel. New areas of the phase diagram of superfluid 3He in aerogel will be explored. The Aerogel may potentially offer the possibility of introducing controlled disorder into the liquid to create new physical systems. One project at Cornell will measure the specific heat of 3He in aerogel near the superfluid transition. Another Cornell project will study coherent spin precession in pure 3He under specific field gradient conditions that yield a long-lived homogenous precession mode. A collaboration at the Kapitza Institute in Moscow will examine the feasibility of stabilizing the B phase of 3He in Aerogel, as well as explore the spin dynamics in the presence of disorder. At Delaware, the collaboration will focus on exploring the feasibility of new tailor made aerogels, having correlations that are different from those grown under basic conditions. The Delaware group will also examine the feasibility of subjecting the aerogel to uniaxial compression to alter the density and provide a preferred direction into the aerogel. Theoretical support for these activities will be provided by the group at the Ohio State University and by researchers at the Kapitza Institute. Graduate students and post-doctoral associates involved in this project will be exposed to sensitive signal detection and recovery technology, large scale project design and management as well as a thorough exposure to data acquisition and management. Our substantial involvement in research with colleagues in Russia will provide International perspectives and establish long-term collaborations that are important for the scientific community as a whole. Our training will prepare students and post-docs for academic, technical, and management careers. This work is directed at the study of the superfluid 3He in the presence of disorder. While ordinarily, superfluid 3He is the purest material on earth and supports no disorder or impurities, we have found that the introduction of a dilute nanometer scale structured silica glass allows the properties of the superfluid to be altered in a well-defined way. The changes to the phase diagram, including the ability to support new types of magnetic (spin) transport mechanisms will be explored in this project which is to be carried out at Cornell University in Ithaca, the University of Delaware, the Ohio State University, and at the Kapitza Institute in Moscow. The group will develop and use new magnetic imaging and sonic techniques, and carry out sensitive measurements at ultra-low temperatures. The research should provide information on a potentially new class of three dimensional quantum phase transitions (a quantum phase transition is one in which the fluctuations near the critical point are quantum and not thermal in nature, and quantum phase transitions are thought to be related to the early universe) as well as the transport of spins across interfaces in disordered materials, a problem of considerable technological importance. Students and Post-Doctoral Associates in this program receive rigorous training in physics, signal recovery, data acquisition and management as well as project integration, and can pursue careers in either academic or industrial science. The International aspect of our collaboration also offers unique potential for human resources.