Ultracold fermions with repulsive interactions
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An ultracold Fermi gas with repulsive interaction has been studied. For weak interactions, the atomic gas is metastable, and the interactions were characterized by obtaining the isothermal compressibility from atomic density profiles. For stronger interactions (k[subscript F]a ≈ 1), rapid conversion into Feshbach molecules is observed. When the conversion rate becomes comparable to the Fermi energy divided by η, the atomic gas cannot reach equilibrium without forming pairs. This precludes the predicted transition to a ferromagnetic state (Stoner transition). The absence of spin fluctuations proves that the gas stays paramagnetic. In free space, a Fermi gas with strong short-range repulsion does not exist because of the rapid coupling to molecular states.
DepartmentMassachusetts Institute of Technology. Department of Physics
EPJ Web of Conferences
Ketterle, W. “Ultracold Fermions with Repulsive Interactions.” Edited by O. Dulieu, P. Grangier, M. Leduc, and H. Perrin. EPJ Web of Conferences 57 (2013): 01001.
Final published version