Superfluid Signatures in a Dissipative Quantum Point Contact

Area of Science:

• Quantum physics
• Condensed matter physics
• Atomic physics

Background:

• Superfluidity in strongly interacting Fermi gases is crucial for understanding quantum many-body phenomena.
• Quantum point contacts are essential for probing transport properties in mesoscopic systems.
• Particle loss introduces dissipation, significantly altering quantum transport characteristics.

Purpose of the Study:

• To investigate the impact of local, spin-dependent particle loss on superfluid transport in fermionic lithium atoms.
• To explore the transition from non-Ohmic to Ohmic superfluid transport under increasing dissipation.
• To model the observed transport phenomena using a theoretical framework.

Main Methods:

• Experimental measurement of superfluid transport through a quantum point contact using fermionic lithium atoms.
• Introduction of local, spin-dependent particle loss as a source of dissipation.
• Development of a theoretical model involving mean-field reservoirs and a dissipative site.
• Application of the Keldysh formalism for nonequilibrium calculations.

Main Results:

• Observed a transition from characteristic non-Ohmic superfluid transport to excess Ohmic current as dissipation strength increased.
• The transition point was identified when dissipation exceeded the superfluid gap.
• The developed model successfully reproduced the observed nonequilibrium particle current.

Conclusions:

• Local particle loss fundamentally alters superfluid transport in strongly interacting Fermi gases.
• The transition to Ohmic behavior is linked to dissipation overcoming the superfluid gap.
• While the particle current is explained, the model requires further refinement to fully account for the observed loss rate and spin current.