Bragg spectroscopy and Ramsey interferometry with an ultracold Fermi gas

Abstract

We report on the observation of Bragg scattering of an ultracold Fermi gas of 6Li atoms at a dynamic optical potential. The momentum states produced in this way oscillate in the trap for time scales on the order of seconds, nearly unperturbed by collisions, which are absent for ultracold fermions due to the Pauli principle. In contrast, interactions in a mixture with 87Rb atoms lead to rapid damping. The coherence of these states is demonstrated by Ramsey-type matter wave interferometry. The signal is improved using an echo pulse sequence, allowing us to observe coherence times longer than 100 mus. Finally we use Bragg spectroscopy to measure the in-situ momentum distribution of the 6Li cloud. Signatures for the degeneracy of the Fermi gas can be observed directly from the momentum distribution of the atoms inside the trap.

19 pages, 10 figures

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Cited by in corpus (5)

• Contact and sum-rules in a near-uniform Fermi gas at unitarity
• Rabi Interferometry and Sensitive Measurement of the Casimir-Polder Force with Ultra-Cold Gases
• Velocimetry of cold atoms by matterwave interferometry
• Spectroscopic Bogoliubov features near the unitary limit
• Calibrating the momentum width of a trapped Bose-Einstein condensate by one-dimensional optical lattice pulse sequences