Optical Control of Magnetic Feshbach Resonances by Closed-Channel Electromagnetically Induced Transparency.

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Gases
• Ultracold Atomic Systems

Background:

• Magnetic Feshbach resonances are crucial for controlling interactions in ultracold atomic gases.
• Optically trapping lithium-6 (⁶Li) Fermi gases allows for precise experimental studies.
• Controlling Feshbach resonances is essential for creating and manipulating quantum states.

Purpose of the Study:

• To demonstrate control over magnetic Feshbach resonances in optically trapped ⁶Li Fermi gases.
• To investigate the use of two optical fields to create a dark state in the closed molecular channel.
• To reduce light-induced loss rates for broad Feshbach resonances.

Main Methods:

• Utilizing two optical fields to create a dark state in the closed molecular channel of a ⁶Li Fermi gas.
• Tuning narrow Feshbach resonances by up to 3 Gauss.
• Employing a new model of light-induced loss spectra with continuum-dressed basis states.

Main Results:

• Achieved a spontaneous lifetime increase to 0.4 s for broad resonances at the dark-state resonance, a significant improvement over 0.5 ms with single-field tuning.
• Developed a model that accurately predicts loss spectra for both broad and narrow resonances.
• Demonstrated that the two-field method substantially reduces two-body loss rates compared to single-field methods for the same tuning range.

Conclusions:

• The two-field method offers enhanced control over magnetic Feshbach resonances in ⁶Li Fermi gases.
• This technique significantly mitigates two-body loss, enabling longer coherence times and improved quantum state manipulation.
• The developed model provides accurate predictions for loss spectra, aiding future experimental design.