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

A remarkable set of universal relations is known to directly connect thermodynamic and microscopic properties of interacting Fermi gases. So far, these contact relations have been established only for interactions with s-wave symmetry, i.e., with zero relative angular momentum. We report measurements of two new physical quantities, the p-wave contacts, and present evidence [1] that they encode the universal aspects of p-wave interactions through recently proposed relations [2,3]. Our experiments use a spin-polarized ultracold Fermi gas of $^{40}$K, in which s-wave interactions are suppressed, while p-wave interactions are enhanced near a Feshbach resonance. Using time-resolved spectroscopy and momentum distribution measurements, we study how correlations in the system develop after quenching the atoms into an interacting state. Combining quasi-steady-state measurements with new contact relations, we infer an attractive p-wave interaction energy as large as the Fermi energy. Our results reveal new ways to understand and characterize the properties of resonantly interacting p-wave quantum gases. [1] C. Luciuk et al., Nature Phys. to appear (2016); [2] S. M. Yoshida, M. Ueda, PRL 115, 135303 (2015); [3] Zhenhua Yu, J. H. Thywissen, Shizhong Zhang, PRL 115, 135304 (2015).