Emergent 𝑠-wave interactions in orbitally active quasi-two-dimensional Fermi gases

Orbital degrees of freedom are natural in electronic materials, reflecting the valence structure of their atomic constituents. Conversely, neutral atoms in optical lattices typically occupy the lowest-energy band and interact through 𝑠-wave interactions. Pioneering experiments employing excited orbital bands have revealed new phenomena including chiral many-body states . Furthermore, theoretical work suggests new types of quantum simulation and rich physics of extended Hubbard models.

Publication Date: 15 November, 2024

Authors: C. J. Dale, K. G. S. Xie, K. Pond Grehan, Shizhong Zhang, J. Maki, and J. H. Thywissen

Abstract:

We investigate the scattering properties and bound states of a quasi-two-dimensional (Q2D) spin-polarized Fermi gas near a 𝑝-wave Feshbach resonance. Strong confinement promotes the out-of-plane spatial wave function to an orbital degree of freedom with an energetic gap. Employing radio-frequency (rf) spectroscopy, we observe both power-law scaling and the dimensional-crossover feature that are indicative of an emergent 𝑠-wave interaction channel. Additionally, we demonstrate the formation of two types of low-energy dimers, possessing either 𝑠-wave or 𝑝-wave symmetry, through rf spin-flip association from an orbital mixture. Our observations are compared to predictions from a Q2D scattering model that incorporates exchange-antisymmetric orbital pair wave functions. These findings underscore how gapped orbital degrees of freedom can control scattering symmetry in strongly confined ultracold gases.

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