Dynamics of interacting fermions under spin–orbit coupling in an optical lattice clock


Quantum statistics and symmetrization dictate that identical fermions do not interact via s-wave collisions. However, in the presence of spin–orbit coupling (SOC), fermions prepared in identical internal states with distinct momenta become distinguishable. The resulting strongly interacting system can exhibit exotic topological and pairing behaviours, many of which are yet to be observed in condensed matter systems. Ultracold atomic gases offer a promising pathway for simulating these rich phenomena, but until recently have been hindered by heating and losses. Here we enter a new regime of many-body interacting SOC in a fermionic optical lattice clock (OLC), where the long-lived electronic clock states mitigate unwanted dissipation. Using clock spectroscopy, we observe the precession of the collective magnetization and the emergence of spin-locking effects arising from an interplay between p-wave and SOC-induced exchange interactions. The many-body dynamics are well captured by a collective XXZ spin model, which describes a broad class of condensed matter systems ranging from superconductors to quantum magnets. Furthermore, our work will aid in the design of next-generation OLCs by offering a route for avoiding the observed large density shifts caused by SOC-induced exchange interactions.

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Fig. 1: Ramsey spectroscopy with spin-orbit coupling.
Fig. 2: Non-interacting echo decay.
Fig. 3: Spin-orbit coupling with varying interactions.
Fig. 4: Interactions with and without spin–orbit coupling.


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We are grateful to M. Lukin, S. Yelin, V. Gurarie, M. Foster, S. L. Campbell, A. Goban, R. B. Hutson, G.E. Marti, E. Oelker, J. Robinson, L. Sonderhouse and D. G. Reed for stimulating discussions and technical contributions. We thank M. Norcia and A. Kaufman for their careful reading of the manuscript. This research is supported by NIST, DARPA, JILA Physics Frontier Center (NSF-PFC-1125844), AFOSR-MURI, and AFOSR. C.S. is partially supported by the JILA Visiting Fellow Program.

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S.L.B., S.K., T.B., D.K. and J.Y. contributed to the executions of the experiments. A.S.-N., M.L.W. and A.M.R. developed the theory model. All authors discussed the results, contributed to the data analysis and worked together on the manuscript.

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Correspondence to S. L. Bromley.

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Bromley, S.L., Kolkowitz, S., Bothwell, T. et al. Dynamics of interacting fermions under spin–orbit coupling in an optical lattice clock. Nature Phys 14, 399–404 (2018). https://doi.org/10.1038/s41567-017-0029-0

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