Emergent s -Wave Interactions between Identical Fermions in Quasi-One-Dimensional Geometries

• Published in: Physical review. X Vol. 13; no. 2; p. 021013
• Main Authors: Jackson, Kenneth G., Dale, Colin J., Maki, Jeff, Xie, Kevin G. S., Olsen, Ben A., Ahmed-Braun, Denise J. M., Zhang, Shizhong, Thywissen, Joseph H.
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 01.04.2023
• Subjects: Antisymmetry; Atoms & subatomic particles; Collisions; Confinement; Degrees of freedom; Electronic systems; Exchanging; Fermions; Optical traps; Particle physics; Resonance; Scattering; Superconductors; Symmetry; Ultracold atoms; Wave functions; Wave interaction
• ISSN: 2160-3308; 2160-3308
• DOI: 10.1103/PhysRevX.13.021013

Orbital degrees of freedom play an essential role in metals, semiconductors, and strongly confined electronic systems. Experiments with ultracold atoms have used highly anisotropic confinement to explore low-dimensional physics, but they typically eliminate orbital degrees of freedom by preparing atoms in the motional ground states of the strongly confined directions. Here, we prepare multiband systems of spin-polarized fermionic potassium (K40) in the quasi-one-dimensional (q1D) regime and quantify the strength of atom-atom correlations using radio-frequency spectroscopy. The activation of orbital degrees of freedom leads to a new phenomenon: a low-energy scattering channel that has even particle-exchange parity along the q1D axis, as if the underlying interactions weres-wave. This emergent exchange symmetry is enabled by orbital singlet wave functions in the strongly confined directions, which also confer high-momentum components to low-energy q1D collisions. We measure both the q1D odd-wave and even-wave “contact” parameters for the first time and compare them to theoretical predictions of one-dimensional many-body models. The strength and spatial symmetry of interactions are tuned by ap-wave Feshbach resonance and by transverse confinement strength. Near resonance, the even-wave contact approaches its theoretical unitary value, whereas the maximum observed odd-wave contact remains several orders of magnitude below its unitary limit. Low-energy scattering channels of multi-orbital systems, such as those found here, may provide new routes for the exploration of universal many-body phenomena.