Emergent s-wave interactions in low-dimensional systems of a spin-polarized Fermi gas

Ultracold atom experiments in low dimensions often work in regimes where motional ground states are prepared in strongly confined degrees of freedom. In this work, we study interactions near a p-wave Feshbach resonance in a spin-polarized gas of fermionic Potassium-40. One- and two-dimensional optical lattices confine our gas, creating quasi-two- and quasi-one-dimensional systems, respectively. The crucial new element of our investigations is the activation of orbital degrees of freedom by allowing population in multiple bands of the confinement lattice. We find that atoms orbitally excited in the strongly confined directions scatter with emergent s-wave character with atoms in the ground orbital state. Scattering resonances occur at energies displaced by the orbital excited-state energy from the underlying p-wave resonance energy. The resonances are characterized with radio-frequency (rf) dimer association measurements and rf spectroscopy. A multi-band model of scattering is used to predict dimer energies for each resonance. Correlations in the gas are related to the high-frequency tail of rf spectroscopy, and match the predicted scaling for s- and p-wave resonances. Our investigations of emergent s-wave scattering in multiple low-dimensional geometries may provide new routes for exploring universal many-body phenomena.