Phase Separation and Pair Condensation in a Spin-Imbalanced 2D Fermi Gas

Area of Science:

• Quantum gases
• Condensed matter physics
• Atomic physics

Background:

• Two-component Fermi gases are crucial for understanding many-body quantum phenomena.
• Spin imbalance introduces complex interactions and potential phase transitions.

Purpose of the Study:

• Investigate phase separation and superfluidity in quasi-two-dimensional Fermi gases with imbalanced spin populations.
• Characterize the nature of pair condensates under varying interaction strengths and polarizations.

Main Methods:

• Utilized a two-component quasi-two-dimensional Fermi gas.
• Probed system at different interaction strengths and polarizations.
• Measured in-trap densities and pair momentum distributions after time-of-flight expansion.

Main Results:

• Observed in-trap phase separation, forming a spin-balanced core within a polarized gas, across various experimental parameters.
• Detected pair condensation in momentum space for imbalanced gases, even at high polarizations where phase separation disappears.
• Evidence for a polarized pair condensate was found.

Conclusions:

• The study reveals the coexistence of phase separation and pair condensation in 2D spin-imbalanced Fermi gases.
• The observation of zero-momentum pair condensates suggests new avenues for exploring exotic superfluid phases in lower dimensions.