Materials World Network: Nearly Two Dimensional 3He- A New Model Quantum System

Cornell University, Ithaca NY

Investigators

Abstract

Technical Abstract This Materials World Network award by the Division of Materials Research supports a three-year experimental program to investigate how reducing the dimensionality of 3He leads to novel p-wave order parameters when this unconventionally paired superfluid is confined to a length comparable to the coherence length. In contrast to metallic systems, 3He has a spherical Fermi surface; yet anisotropic paired states emerge from the isotropic normal liquid. Confinement of 3He in small geometries is expected to modify this behavior. It has been theoretically predicted that confined superfluid 3He will exhibit broken translational symmetry en route to the destruction of superfluidity. Dimensional constraints might also promote the stability of competing phases that are not manifest in the bulk. The technology to fabricate confining geometries with well characterized surfaces that can be patterned to achieve specified roughness has been developed at Cornell University. The roughness will affect the resulting phases via their stability and response to disorder ? an important feature that has implications for the broader relevance of this work to Condensed Matter Physics. Patterning to introduce periodicity and test the robustness of emerging phases of confined 3He against periodicity is also planned. We will also construct and use high precision flow cells to examine flow of 4He, 3He doped 4He films and eventually superfluid 3He in nanoporous media. These demanding experiments, which require development of new techniques, provide a challenging environment where graduate and undergraduate students acquire skills (the ability to innovate, initiate, design and carry out) as well as become familiar with analytic and display tools to prepare them for careers in the Nation's scientific and technological infrastructure. The research program will be integrated with partner programs at Royal Holloway University of London and Manchester University. Graduate students will have the opportunity to work with their counterparts by spending a semester in the UK and by hosting counterparts at Cornell. The research program will also incorporate an undergraduate student throughout the award period. Non-Technical Abstract Helium (unlike all other elements) is inherently quantum-mechanical and does not solidify (unless compressed) even down to absolute zero temperature. It is one of the purest materials that can be prepared by any means, since at these temperatures, impurities simply freeze out during the procedures required to obtain the liquid state. Eventually 3He attains a highly ordered state: superfluidity, which is different from that attained in most superconductors and its sister isotope 4He. The magnetism of the superfluid atoms means that the atoms pair up together and undergo orbital motion exhibiting different phases. These behaviors are affected by confining 3He within precisely characterized geometries that effectively alter the dimensionality of the 3He. By carrying out precise measurements on these systems the research will add to our understanding of the role of confinement under less extreme conditions. The program will also prepare graduate students for an increasingly international scientific and technological environment by embedding them in (and allowing them to host students from) counterpart laboratories that use different techniques to probe the same systems. Besides adding to the understanding of quantum systems, this research provides a demanding experimental environment that educates and trains graduate and undergraduate students for successful careers in the Nation's scientific and technological infrastructure. In addition, this research program will also create a positive impact on future science and technology workforce by involving a science teacher in this research during summer.