Magneto-Acoustic and Quantum Transport in Helium Three

Northwestern University, Evanston IL

Investigators

Abstract

TECHNICAL SUMMARY: This award supports research and education in theoretical condensed matter physics in magneto-acoustic and quantum transport in helium three. The theoretical investigations describe and explain newly discovered and newly predicted quantum condensed phases of matter. The research responds to recent experimental results establishing the existence of new superfluid phases of 3He in confined geometries and the existence of new collective modes of superfluid 3He exhibiting unusual magneto-acoustic properties, including acoustic birefringence of transverse sound. Transverse magneto-optical phenomena have been recently observed in electronic superconductors. The theoretical efforts address predicting and characterizing the magneto-optical and magneto-acoustic properties of quantum condensed phases of 3He. Another vein of research develops theory to predict new phases of 3He with properties characteristic of both solid and superfluid states of matter, i.e. ''crystalline order in superfluid 3He''. In particular, the PI will carry out theoretical research based on transport theory for quantum fluids that will examine the physical properties and experimental signatures of this predicted phase of 3He. A third effort employs theoretical models and quantum statistical methods for analyzing the interplay between ordering associated with symmetry breaking phase transitions, and extrinsic disorder that is present in virtually all macroscopic forms of matter. These theoretical developments connect with the experimental systems of liquid 3He impregnated into low-density silica glass, also called aerogel. This system permits theory to compare to a controllable and tunable medium to study effects of quenched random disorder in strongly correlated Fermi liquids. The research has a strong education component involving the training of graduate students and a continuation of the PI's long history of recruiting undergraduates in cutting edge research projects with publishable outcomes. The research connects with substantial international collaborations in Germany and France focused on the research topic, thereby strengthening and enriching the US physical community. NON-TECHNICAL SUMMARY: This award supports research and education in theoretical studies of a unique fluid, helium three, which exhibits magnetic and flow properties governed by the laws of quantum physics. Just as common materials exhibit different phases such as the liquid, gas and solid phases, so do quantum fluids, but the laws of quantum physics allow a wealth of complexities not normally encountered in everyday materials. The theoretical investigations of this research describe and explain newly discovered and newly predicted quantum phases of the fluid. The research responds to recent experimental results establishing the existence of new quantum phases of helium three which occur if the fluid is confined in small regions of space, such as cavities, droplets or films. In these confined geometries the existence of new physical behavior is exhibited as remarkable magnetic properties that appear when sound travels through the droplet or the film of liquid. Such behaviors reflect the quantum laws of nature operating in the liquid. These phenomena allow for a deeper understanding of similar phenomena in the technologically important superconductors, which can carry electricity with no energy loss. The theoretical efforts extend to other geometries that are important for investigating a wide range of quantum behavior, and in expanding basic scientific understanding beyond helium three to superconducting wires, and to practical quantum electronic and magnetic devices that will be part of the next revolution in ultra-miniaturization and quantum computers. The research has a strong education component involving the training of graduate students and a continuation of the PI's long history of recruiting undergraduates in cutting edge research projects with publishable outcomes. The research connects with substantial international collaborations in Germany and France focused on the research topic, thereby strengthening and enriching the US physical community.