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Tuning the Mean-Field Energy in a Fermi Gas of Atoms



C A. Regal, Deborah S. Jin


An exotic superfluid phase has been predicted for an ultracold gas of fermionic atoms. Experimenters have cooled these gases into the quantum degenerate regime and explored collisional effects. However, quantum mechanical many-body interaction phenomena, such as superfluidity or mean-field effects, have not previously been observed. Here we present measurements of the mean-field interaction energy in a quantum degenerate Fermi gas and report on progress toward realizing the predicted reasonance superfluid phase. Starting with a two-component gas that has been evaporatively cooled to quantum degeneracy, we create controllable, strong interactions in the gas using a magnetic-field Feshbach resonance. Near the resonance peak we have directly measured both positive and negative interaction energies using rf spectroscopy. In addition we observe anisotropic expansion, which has recently been suggested as a signature of superfluidity, and show that this can be attributed to a purely collisional effect.


Fermi gas of atoms, superfluidity


Regal, C. and Jin, D. (2021), Tuning the Mean-Field Energy in a Fermi Gas of Atoms, Nature (Accessed March 3, 2024)
Created October 12, 2021