Engineering New Anisotropic Superfluid Phases of 3He

Northwestern University, Evanston IL

Investigators

Abstract

Non-technical Abstract: The proposed project highlights research training of two graduate students. It includes current participation of one local high school student developing state-of-the-art software, science education of student teams from elementary school and from a local high school, and an ongoing research project of an undergraduate student to develop a novel detection instrument for a new generation of nuclear physics experiments. These activities are outgrowths of, and made possible by, the PI's silica aerogel growth laboratory. One success story involves three young 7th grade girls who learned to grow silica alcogels as part of a science competition that won state and then national-regional championships. The present project supports this educational program with mentoring from the PI and his graduate student team. In fact, the central part of the research project is focused on quantum fluids confined within aerogel, an extremely porous glass used to engineer new quantum states of superfluid helium at ultra-low temperatures, a key component of the project. The importance of low temperature research and technology in today's quantum world is that it drives development of instrumentation, pushing limits in temperature ever lower, where the PI's laboratory has made significant contributions. This work supplies a need for trained postdocs and new faculty appointments in experimental condensed matter physics and inspires recruitment of young scientists with background in many body physics, complex symmetry breaking, and quantum phase transitions. Investigation of the superfluid helium-three paradigm provides guidance for solutions to some of the challenging scientific problems of the day, ranging from qubit coherence in quantum information science to materials physics. Technical Abstract: Superfluid helium-three is a known topological quantum condensed system that is predicted to host Majorana fermionic excitations in the form of quasiparticle bound states, a subject of interest to researchers in the field of quantum information science. The proposal, Engineering New Anisotropic Superfluid Phases of Helium-three, is a platform for both basic research and instrumentation development. Today it is known that it is possible to stabilize new types of helium-three superfluid phases exhibiting different spontaneously-broken symmetries by engineering anisotropy through confinement of the superfluid in highly porous, anisotropic, aerogels or in thin films. Each phase has its specific type of orbital and/or spin topological singularities including vortices and superfluid textures of its orbital and spin angular momenta. The surface of the superfluid B-phase, and the vortex cores in the superfluid A-phase, the latter being a chiral phase, are predicted to harbor Majorana fermions of intense interest to researchers in quantum information science. Chirality, in this context, is the combination of loss of mirror symmetry in conjunction with broken time-reversal symmetry, a key property of topological superconductivity. In the proposed work new anisotropic phases of superfluid helium-three are investigated using nuclear magnetic resonance and resonant acoustic cavity techniques for a wide range of magnetic field and temperature. Recent success in the PI's laboratory on which the proposed program builds, is the capability of continuously holding temperatures below 0.001 K, for as long as several months. These extremely efficient refrigerators allow maintenance of quantum coherence over long time scales and offer opportunities for improvement in qubit performance, an essential requirement for quantum information processing. Preliminary results are promising for understanding the unusual interplay of anisotropy and magnetic field. One aspect of this research is motivated by prediction of a topological thermodynamic phase transition of Majorana fermions at the free surface of topological superfluid helium-three-B. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.