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Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics
Published on: August 27, 2013
Critical velocity for superfluid flow across the BEC-BCS crossover.
D E Miller1, J K Chin, C A Stan
1Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, MIT, Cambridge, Massachusetts 02139, USA.
Physical Review Letters
|October 13, 2007
Summary
Critical velocities in ultracold Fermi gases reveal superfluidity is strongest at unitarity, where resonant atomic interactions enhance robustness. Dissipation onset in a moving optical lattice determined these velocities.
Area of Science:
- Quantum gases
- Condensed matter physics
- Ultracold atomic physics
Background:
- Superfluidity in Fermi gases is a key area of condensed matter physics.
- The BEC-Bose-Einstein Condensate to BCS-Bardeen Cooper–Schrieffer crossover allows tuning of superfluid properties.
- Understanding critical velocities is crucial for characterizing superfluid behavior.
Purpose of the Study:
- To investigate critical velocities in ultracold superfluid Fermi gases across the BEC-BCS crossover.
- To determine the conditions under which superfluidity is most robust.
- To study the influence of experimental parameters on critical velocity.
Main Methods:
- Observation of critical velocities in ultracold Fermi gases.
- Utilizing a one-dimensional optical lattice that was moved at varying velocities.
- Measuring the abrupt onset of dissipation to determine critical velocities.
- Studying the dependence on lattice depth and density profiles.
Main Results:
- Critical velocities were observed throughout the BEC-BCS crossover.
- A distinct peak in critical velocity was found at unitarity.
- Superfluidity demonstrated maximum robustness for resonant atomic interactions at unitarity.
- Dependence on lattice depth and inhomogeneous density was characterized.
Conclusions:
- Superfluidity in Fermi gases is maximally robust at unitarity due to resonant interactions.
- Critical velocity measurements provide insight into the limits of superfluidity.
- The study quantifies the influence of lattice parameters on superfluid dissipation.
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