Competition between Spin Echo and Spin Self-Rephasing in a Trapped Atom Interferometer
Résumé
We perform Ramsey interferometry on an ultracold 87Rb ensemble confined in an optical dipole trap. We use a $\pi$-pulse set at the middle of the interferometer to restore the coherence of the spin ensemble by canceling out phase inhomogeneities and creating a spin echo in the contrast. However, for high atomic densities, we observe the opposite behavior: the $\pi$-pulse accelerates the dephasing of the spin ensemble leading to a faster contrast decay of the interferometer. We understand this phenomenon as a competition between the spin-echo technique and an exchange-interaction driven spin self-rephasing mechanism based on the identical spin rotation effect (ISRE). Our experimental data is well reproduced by a numerical model.
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