Broad Feshbach Resonance with a Large Background Scattering Length in a Fermionic Atom-Molecule Mixture
Zhen Su1,2, Tong-Hui Shou1,2, Huan Yang1,2,3
1Hefei National Research Center for Physical Sciences at the Microscale, and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China.
Physical Review Letters
|December 5, 2025
Summary
Researchers observed a broad magnetic Feshbach resonance in ultracold sodium-potassium (NaK) molecules and potassium (K) atoms. This resonance enables studying strongly interacting, mass-imbalanced fermionic gases, potentially revealing new quantum phenomena.
Area of Science:
- Atomic, Molecular, and Optical (AMO) Physics
- Quantum Gases
- Ultracold Matter
Background:
- Ultracold atom-molecule mixtures are crucial for exploring quantum phenomena.
- Feshbach resonances allow tuning of interactions in ultracold gases.
- Studying mass-imbalanced systems presents unique challenges and opportunities.
Purpose of the Study:
- To observe and characterize a broad magnetic Feshbach resonance in a specific ultracold fermionic mixture.
- To investigate the hydrodynamic regime driven by a large background scattering length.
- To explore the potential for studying strongly interacting fermionic gases with mass imbalance.
Main Methods:
- Preparation of an ultracold fermionic mixture of sodium-potassium (NaK) molecules and potassium (K) atoms in their lowest hyperfine states.
- Characterization of the Feshbach resonance by measuring resonantly enhanced loss rates.
- Measurement of elastic scattering cross sections via cross-species thermalization.
Main Results:
- Observation of a broad magnetic Feshbach resonance with a significant background scattering length.
- Demonstration that the large background scattering length drives the system into the hydrodynamic regime.
- Observation of phase-locked, common-frequency oscillations in the center-of-mass motions of atoms and molecules due to hydrodynamic drag.
Conclusions:
- The discovered broad atom-molecule Feshbach resonance provides a new platform for quantum gas research.
- The large background scattering length facilitates access to the hydrodynamic regime.
- This system offers a novel pathway for investigating strongly interacting fermionic gases with mass imbalance.
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