Ultracold field-linked tetratomic molecules.

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Chemistry
• Condensed Matter Physics

Background:

• Ultracold polyatomic molecules are valuable for cold chemistry, precision measurements, and quantum information processing due to their complex structures.
• Conventional cooling techniques face challenges with the increased complexity of polyatomic molecules compared to diatomics.

Purpose of the Study:

• To demonstrate a novel approach for creating weakly bound ultracold polyatomic molecules.
• To utilize electroassociation in a degenerate Fermi gas of microwave-dressed polar molecules via field-linked resonance.

Main Methods:

• Starting with ground-state Sodium-Potassium (NaK) molecules.
• Employing electroassociation through a field-linked resonance in a degenerate Fermi gas of microwave-dressed polar molecules.
• Directly imaging dissociated tetramers using microwave-field modulation.

Main Results:

• Successfully created approximately 1.1 × 10^3 weakly bound tetratomic (NaK)2 molecules.
• Achieved a phase space density of 0.040(3) at 134(3) nK, over 3,000 times colder than previous tetratomic molecules.
• Observed a maximum tetramer lifetime of 8(2) ms, demonstrating collisional stability even in an optical dipole trap.

Conclusions:

• The demonstrated electroassociation method is a universal tool for assembling weakly bound ultracold polyatomic molecules from smaller polar molecules.
• This is a critical step towards Bose-Einstein condensation of polyatomic molecules and a crossover from a dipolar superfluid to a tetramer Bose-Einstein condensate.
• The long-lived field-linked state serves as an ideal precursor for deterministic optical transfer to deeply bound tetramer states.