Contact and Sum Rules in a Near-Uniform Fermi Gas at Unitarity

Area of Science:

• Quantum gases
• Atomic physics
• Condensed matter physics

Background:

• Unitary Fermi gases are strongly interacting quantum systems.
• Superfluidity in Fermi gases is a key phenomenon in many-body physics.
• Understanding their thermodynamic properties is crucial.

Purpose of the Study:

• To experimentally investigate the high-energy excitation spectra of unitary Fermi gases.
• To measure the dynamic structure factor across the superfluid transition.
• To determine the universal contact parameter and internal energy.

Main Methods:

• Focused beam Bragg spectroscopy was used to probe the central region of trapped atomic clouds.
• Measurements were performed at temperatures below and above the superfluid transition.
• Sum rules were applied to the measured Bragg spectra.

Main Results:

• The dynamic structure factor was measured for unitary Fermi gases.
• The universal contact parameter (C) behavior across the superfluid transition was resolved.
• The internal energy of the gases at unitarity was obtained using the kinetic sum rule.

Conclusions:

• The study provides experimental insights into the excitation spectra of unitary Fermi gases.
• The universal contact parameter's behavior across the superfluid transition was experimentally confirmed.
• The work validates theoretical approaches for calculating thermodynamic properties.