Exploring dipolar many body effects in a degenerate molecular Fermi gas

The interplay of quantum statistics and long-range dipole interactions in degenerate Fermi gases enables the exploration of exotic many-body phenomena. We present our progress in studying Fermi surface deformation (FSD) of ultracold polar molecules [1-3], a quantum effect where anisotropic interactions reshape the momentum distribution of a degenerate Fermi gas.

To probe dipolar molecular Fermi gas at low temperatures, we employ a dual-color microwave (MW) shielding [4] in our system of fermionic ²³Na⁴⁰K molecules to reduce the inelastic losses to 2 ×10¹³ cm³ s^-1 at 400 nK temperature, almost 3 times lower than that with circular-only MW shielding. This allows us to evaporatively cool the molecular sample to 0.25 times the ​Fermi temperature of the gas. By tuning the ellipticity of the circular MW field, we break the angular symmetry of the intermolecular potential [5], inducing anisotropic dipolar interactions in the plane of the circular MW. This results in FSD, with the deformation direction and magnitude controllable via the circular MW field's handedness and ellipticity, respectively. This work opens new avenues for investigating strongly interacting dipolar Fermi gases with tunable anisotropic interactions.

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2. Velijic et al., New J. Phys. 20, 093016 (2018)

3. Velijic et al., Phys. Rev. Research 1, 012009(R) (2019)

4. Bigagli et al., Nature vol 631, 289–293 (2024)

5. Chen et al., Nature vol 614, 59–63 (2023)