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Sound Propagation and Quantum-Limited Damping in a Two-Dimensional Fermi Gas.
Markus Bohlen1,2,3, Lennart Sobirey1, Niclas Luick1
1Institut für Laserphysik, Universität Hamburg, Luruper Chaussee 149, Hamburg 22761, Germany.
Physical Review Letters
|July 9, 2020
Summary
This study investigates strongly interacting two-dimensional Fermi gases by examining sound wave propagation. The research reveals minimal damping in the strongly interacting regime, approaching a perfect fluid
Area of Science:
- Condensed Matter Physics
- Quantum Gases
- Many-Body Physics
Background:
- Strongly interacting two-dimensional Fermi systems present significant challenges due to local correlations and fluctuations.
- Understanding their thermodynamic and transport properties is crucial for advancing many-body physics.
Purpose of the Study:
- To probe thermodynamic and transport properties of a 2D Fermi gas across the BEC-Bose Einstein Condensate–BCS Bardeen-Cooper-Schrieffer crossover.
- To investigate sound mode propagation and damping to reveal system characteristics.
Main Methods:
- Exciting particle currents by imprinting a phase step onto homogeneous Fermi gases in a box potential.
- Extracting the speed of sound from density oscillation frequencies.
- Measuring sound mode damping, related to viscosity and thermal conductivity.
Main Results:
- The speed of sound was measured across the BEC-BCS crossover, showing agreement between dynamic measurements, static measurements, and quantum Monte Carlo calculations.
- Sound mode damping was found to be minimal in the strongly interacting regime.
- Diffusivity was observed to approach the universal quantum bound of a perfect fluid (ℏ/m).
Conclusions:
- Sound mode analysis provides a dynamic method to measure the equation of state in 2D Fermi gases.
- The strongly interacting regime exhibits near-perfect fluid behavior with minimal damping.
- This research offers insights into the fundamental properties of strongly correlated quantum systems.
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