3He in Confinement

Northwestern University, Evanston IL

Investigators

Abstract

Nontechnical Abstract: At very low temperatures all matter enters a regime described only by quantum mechanics where the states of matter are called quantum states. Some of these states allow electron currents to flow that are completely frictionless and in helium liquids the atoms can flow without generating any heat, and are called superfluids. In this project new classes of the superfluid of the light isotope of helium, helium-three, are engineered in anisotropic confinement using extremely small-scale porous glass prepared in the project laboratory. The topology of these states allows storage of quantum information which is an essential component of the quantum calculations that promise a revolution in computer technology. Both the low temperatures and the topology of the quantum states are essential. Graduate students and undergraduates, as well as some high school students, learn the specialized techniques that are required to make the porous glass materials and characterize them using scanning electron microscopy, cryogenics, and optical methods to achieve the project goals: creating and identifying new topological quantum states of liquid helium. High quality samples are also provided for collaborations with other laboratories in the USA, France, Japan, and the United Kingdom for a range of research applications on quantum fluids. Furthermore, an active software based tool on our website is developed and maintained by graduate students, to make accessible the physical properties of the superfluids we study. The PI continues advocacy for public awareness of helium as a precious natural resource serving on the recently convened APS, ACS, and MRS sponsored Helium Economics Committee, and appearances before congress, on national television, for science magazines, and at invited talks at international conferences and workshops. Technical Abstract: This project for graduate student research includes the search for new quantum states with engineered symmetry among the manifold of possible fermionic p-wave 3He superfluids. Nano-structured environments from dense arrays of small pores in alumina membranes are used to define specific anisotropic environments and cooled to ultra-low temperatures for investigation using ultra-sound and high resolution NMR. A second part of the project is to use high porosity silica aerogel that is fabricated with controlled anisotropy. With this approach the recent predictions for such new states of matter are tested, particularly the interplay of states with chiral and non-chiral symmetry. The topology of such superfluids support Majorana excitations that have been proposed as a key component of quantum information processing and has a direct connection to topological superconductors. A central aspect of the theory is that anisotropic environments can stabilize anisotropic superfluid states. There is already an indication of this in superfluid 3He that parallels the behavior of the topological superconductor UPt3. In the project's research control of the surface conditions are performed using single atom layers of the bosonic superfluid 4He. Additionally, acoustic resonant cavities are produced using nanofabrication facilities. The project supports continuing funding for graduate education and undergraduate research in experimental physics.