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Universal quantum viscosity in a unitary Fermi gas.
Science (New York, N.Y.)
|December 15, 2010
Summary
Researchers explored universal hydrodynamics in a Fermi gas of atoms. They measured shear viscosity at low and high temperatures, finding precise T(3/2) scaling at high temperatures and comparing it to perfect fluid behavior.
Area of Science:
- Quantum physics
- Condensed matter physics
- Atomic physics
Background:
- A Fermi gas with resonant interactions is theoretically predicted to exhibit universal hydrodynamics.
- Transport coefficients, like shear viscosity, are expected to be universal functions of density and temperature.
Purpose of the Study:
- To experimentally measure the shear viscosity of a Fermi gas at both low and high temperatures.
- To verify the predicted universal hydrodynamic behavior and temperature scaling of viscosity.
Main Methods:
- Low-temperature shear viscosity was measured using breathing mode damping.
- High-temperature shear viscosity was determined by analyzing the anisotropic expansion of the atomic cloud.
- Universal hydrodynamic equations, incorporating friction and heating, were employed to extract viscosity values.
Main Results:
- Shear viscosity was measured across different temperature regimes.
- Precise T(3/2) scaling of viscosity was observed at high temperatures.
- The ratio of shear viscosity to entropy density was estimated and compared to theoretical predictions for a perfect fluid.
Conclusions:
- Experimental measurements support the theory of universal hydrodynamics in Fermi gases.
- The study provides quantitative data on shear viscosity and its temperature dependence.
- Findings contribute to understanding the quantum nature of transport properties in strongly interacting systems.
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