Evidence for universal relations describing a gas with p-wave interactions

Abstract

In dilute gases, a set of universal relations, known as the contact relations, directly connects thermodynamics and microscopic properties. So far, they have been established only for interactions with s-wave symmetry—that is, without relative angular momentum. Here we report measurements of two new physical quantities, the p-wave contacts, and, using recently proposed relations, present evidence that they encode the universal aspects of p-wave interactions. Our experiments use an ultracold Fermi gas of 40K, in which s-wave interactions are suppressed by polarizing the sample, whereas p-wave interactions are enhanced by working near a scattering resonance. Using time-resolved spectroscopy, we study how correlations in the system develop after quenching the atoms into an interacting state. By combining quasi-steady-state measurements with new contact relations, we infer an attractive p-wave interaction energy as large as half the Fermi energy. Our results reveal new ways to understand and characterize the properties of a resonant p-wave quantum gas.

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Figure 1: Tuning p-wave interactions in 40K.
Figure 2: Observation of the p-wave contacts.
Figure 3: The p-wave contacts near two Feshbach resonances.
Figure 4: Dynamics of the p-wave contact and atom number close to resonance.

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Acknowledgements

We thank F. Chevy for discussion and shared notes concerning F versus δBm. We also thank N. Zuber for experimental assistance, and J. Bohn, B. Ruzic, S. Tan, E. Taylor, P. Zhang and Q. Zhou for discussion. This work was supported by AFOSR under FA9550-13-1-0063, ARO under W911NF-15-1-0603, the Croucher Foundation, RGC under under 17306414, NKBRSFC, NSERC and NSFC under 11474179, and the Tsinghua University Initiative Scientific Research Program.

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C.L., S.S. and S.T. performed the experiments. C.L., S.S., S.T. and J.H.T. analysed the data. All authors contributed to the interpretation of the spectra. Z.Y., S.T. and S.Z. developed the two-channel model of the dynamics. All authors contributed to the preparation of the manuscript.

Corresponding authors

Correspondence to Shizhong Zhang or Joseph H. Thywissen.

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The authors declare no competing financial interests.

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Luciuk, C., Trotzky, S., Smale, S. et al. Evidence for universal relations describing a gas with p-wave interactions. Nature Phys 12, 599–605 (2016). https://doi.org/10.1038/nphys3670

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