Strongly correlated superfluid order parameters from dc Josephson supercurrents.

Area of Science:

• Condensed Matter Physics
• Quantum Fluids
• Atomic Physics

Background:

• The direct-current (dc) Josephson effect is a quantum phenomenon crucial for probing the nature of superfluidity.
• Understanding superfluid order parameters in strongly interacting systems is a key challenge in condensed matter physics.

Purpose of the Study:

• To observe and characterize dc Josephson supercurrents in strongly interacting fermionic superfluids.
• To investigate the relationship between Josephson transport and superfluid order parameters in a tunable atomic system.

Main Methods:

• Fabrication of a tunneling junction in a strongly interacting fermionic superfluid.
• Measurement of dc Josephson supercurrents and the current-phase relation across the junction.
• Analysis of the zero-resistance state and its breakdown as a function of junction parameters.

Main Results:

• Observation of dc Josephson supercurrents in fermionic superfluids without applied voltage.
• Confirmation of a sinusoidal current-phase relation for strong tunneling barriers, consistent with Josephson's prediction.
• Determination of the pair condensate fraction across the Bardeen-Cooper-Schrieffer to Bose-Einstein condensation crossover.

Conclusions:

• Coherent Josephson transport provides a sensitive probe for superfluid order parameters in diverse atomic systems.
• The observed phenomena are robust even in the presence of strong electronic correlations.
• This technique offers a new pathway for investigating quantum fluids and their fundamental properties.