New Superfluid States of 3He in Coherence Length Scale Nanofabricated Geometries

Cornell University, Ithaca NY

Investigators

Abstract

****Technical abstract**** The intellectual impact of the understanding of superfluid 3He extends across many fields in Physics. The program funded in this proposal will combine the field of nanofluidics with low temperature physics, to expose new size effects in a quantum fluid. By examination of the flow behavior of the quantum fluid the researchers seek to understand the influence of surface roughness on quantum transport. They will characterize the surface roughness necessary to allow the fluid to be locked to the surface or to slip at the surface. The surface roughness should also add quantifiable disorder to the quantum fluid. In planned experiments, the effect of confinement on the phase diagram will be examined with a view to exposing new (perhaps even handed or chiral) phases. The compressibility of 3He will allow the length scale of the coherence length to be pressure-tuned. By combining low temperatures and nano fabrication, two graduate students and several undergraduates will be exposed to the exciting training ground that has prepared scientists for lead roles in academia and high-technology industries. The proposed research will expose the stability of the superfluid order parameter to confinement, and look for new forms of superfluid under confinement on the way to a quantum phase transition where the superfluidity is extinguished. Such new superfluids might be of interest in quantum computation, and exposing in new types of vorticity. ****Non-Technical Abstract**** Many of our everyday devices (think of cellphones, computers) originate from fundamental advances engendered by condensed matter research. In turn, future advances will rely on exploration of new regimes presently accessible only in a laboratory environment. The research to be conducted in this program will examine the special properties of superfluid 3He when confined in ultra small engineered cavities less than a thousandth of a millimeter tall, marking the transition from bulk 3 dimensional behavior to a new 2 dimensional regime. The flow of helium in these cavities should be dominated by the roughness of the surface and will slip if the surface is too smooth, or will be locked to the surface if the roughness is "just right". By examining flow, the researchers hope to better understand how quantum (as opposed to classical) fluids are different from each other. Quantum fluids display a "graininess" rather than a continuous behavior, and this quantum behavior is emphasized in reduced dimensions because the "grain" size increases. The reduced size will also be exploited in other ways to demonstrate new types of superfluid states that may show handedness like a spinning top. By combining low temperatures and nano fabrication, two graduate students and several undergraduates will be exposed to the exciting training ground that has prepared scientists for lead roles in academia and high-technology industries. The project will test what size range is relevant for the transformation from ordinary 3 Dimensional behavior to 2 Dimensional behavior.