Superfluid Macroscopic Quantum Effects

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****NON-TECHNICAL ABSTRACT****Superfluiid helium is an exotic state of matter wherein normal sized samples of liquid exhibit some of the strange features of the quantum world of atoms. This individual investigator award supports a project focusing on the so-called Josephson effects. Superfluid helium is pushed through an array of thousands of nanometer-sized holes drilled in a thin partition. Unlike ordinary fluids that would simply flow through the holes at a rate proportional to the pushing force, the superfluid moves to and fro within the holes with, on the average, no liquid passing through the holes. The harder one pushes, the faster the vibrations occur. If the apertures are smaller than a characteristic length, basic theory explains why this oscillatory flow should occur in a single aperture. However, it remains a mystery why this oscillatory flow occurs in all the apertures in an array synchronously. It is also a mystery why the vibrations occur even for hole sizes bigger than those predicted by theory. The central goal of the project is to solve these mysteries and further, to exploit the phenomena to create a new class of ultra-sensitive instruments that will be useful in physics, earth studies and navigation. Not only will this project train graduate students and postdoctoral researchers in ideas at the forefront of science, but the skills in instrumentation and nano-fabrication that they will learn to carry out the experiments are in great demand in industry and academia.****TECHNICAL ABSTRACT****Superfluid Helium constrained within an array of thousands of nano-apertures exhibits a variety of Josephson phenomena including a sine-like current-phase relation as well as synchronous dissipative phase slippage, occurring at the Josephson frequency. These features have been exploited to show macroscopic quantum interference effects induced by rotation and heat induced flow. The central goals of this individual investigator project are twofold: 1. to understand the origin of the synchronicity across an array and 2. to determine how to make arrays with characteristics most suitable for use in quantum interferometers devoted to rotation sensing and probing novel physical interactions. Initially an empirical approach will be pursued to determine the characteristics of arrays with various aperture sizes and patterns. These results will be compared to theory. Ultimately sensitive superfluid interferometers to probe exotic physical effects such as an Aharonov-Bohm phase shift in neutral matter will be developed. Along with knowledge at the frontiers of science, PhD students and postdoctoral researchers will learn techniques of nanofabrication, cryogenics, electronic instrumentation and computer control.