Dimer-Projection Contact and the Clock Shift of a Unitary Fermi Gas

Area of Science:

• Quantum physics
• Ultracold atomic gases
• Strongly interacting Fermi systems

Background:

• Short-range correlations are key in Fermi gases but difficult to measure.
• Existing methods are limited to equilibrium or slow dynamics.
• The contact parameter quantifies these correlations.

Purpose of the Study:

• To develop a rapid spectroscopic technique for measuring short-range correlations.
• To enable contact parameter measurements on microsecond timescales.
• To investigate multichannel effects in unitary Fermi gases.

Main Methods:

• Developed a rapid spectroscopic technique using dimer-state projection.
• Applied the technique to ultracold ^{40}K atoms near a Feshbach resonance.
• Measured the contact parameter via radio-frequency spectroscopy and dimer-projection feature scaling.

Main Results:

• Achieved contact measurements on the microsecond timescale, faster than the inverse Fermi energy.
• Demonstrated that the dimer-projection feature strength scales with the contact parameter.
• Provided the first experimental bound on the clock shift of the unitary Fermi gas.

Conclusions:

• The rapid spectroscopic technique is effective for studying short-range correlations.
• Multichannel effects are crucial and lead to deviations from universal predictions.
• This work opens new research avenues in quantum critical behavior and hydrodynamics.