Quantum Hydrodynamics and Energy Flow in Fermi Gases

North Carolina State University, Raleigh NC

Investigators

Abstract

This project uses laser flash photography to image the nearly frictionless fluid flow and energy flow of a unique ultra-cold atomic gas confined between sheets made of laser light. This special atomic gas has the properties of being "strongly interacting," and "fermionic" which causes it to behave in many ways like a liquid metal. When two clouds of these atoms collide, they bounce off of one another, creating shock waves. These experiments simulate properties of exotic matter in intellectual disciplines well outside atomic physics, including neutron stars and quark-gluon plasmas, which existed microseconds after the Big Bang. The experiments also test theories of super-high temperature superconductors, which operate far above room temperature, enabling energy-saving power lines and magnetically levitated trains. The project provides an ideal learning opportunity and serves to train undergraduate students, graduate students, and post-doctoral associates, who work as a team in a supportive environment with the PI to devise, construct, and perform new experiments, and to theoretically analyze the results. With this broad training, graduating students and post-doctoral associates are well situated to be leaders in tackling research questions that arise in science and engineering. This project will study hydrodynamic transport and energy flow in a Fermi gas of 6Li atoms trapped in designer optical potentials. The potentials will imaged onto the cloud from a digital micro-mirror device (DMD) to control the spatial profiles of the atomic gas density and temperature. Confining the atoms between two repulsive sheet potentials enables in-situ imaging with nearly constant atom density along the line-of-sight direction perpendicular to the sheets. This suppresses unwanted averaging of the measured column density over hydrodynamic and low density ballistic regions, which has plagued previous studies. With tunable interaction strength, this method offers new opportunities to explore concepts that cross interdisciplinary boundaries, including local transport properties of scale-invariant systems, recent conformal field theory predictions of quasi-steady state energy flow between scale-invariant systems at different temperatures, and shock wave formation in strongly interacting fluids. The goals of this project include in-situ measurements of i) 1D hydrodynamic flow, local shear viscosity and thermal conductivity; ii) Energy flow between two scale-invariant clouds at different temperatures; iii) Shock wave formation versus interaction strength, temperature, and density profiles.