Interacting Fermions in Quasi-1D*

We explore the physics of interacting fermions in quasi-1D using $^6$Li confined to a 2D optical lattice. Motivated by recent theory, which suggests the usually severe three-body loss near a $p$-wave Feshbach resonance may be suppressed in 1D [1], we measured the three-body recombination rate of spin-polarized $^6$Li in quasi-1D [2]. We analyze the atom loss as a two-step cascade in which weakly bound dimers form prior to their loss arising from atom-dimer collisions to deeply bound diatomic molecules. We find a possible suppression in the rate of dimer relaxation with strong quasi-1D confinement, and for small field detuning from resonance. The implications for loss suppression due to the closed-channel character of this $p$-wave resonance remains to be fully understood. In addition, we study the effect of strong $s$-wave interactions on collective excitations in the Tomonaga-Luttinger liquid regime with a two-spin mixture of $^6$Li. We previously measured the dynamic structure factor for charge excitations using Bragg spectroscopy [3], while the spin excitations were inaccessible due to heating from spontaneous emission. We reduce the heating by using the narrow-linewidth 2S-3P transition (323 nm) and a two-spin mixture with large energy separation. We measure the spin and charge excitation spectrum, and thus realize the first direct measurement of spin-charge separation with tunable interactions.

 

[1] Lihong Zhou and Xiaoling Cui, Phys. Rev. A 96, 030701 (2017).

[2] Y.-T. Chang, R. Senaratne, D. Cavazos-Cavazos, and R. G. Hulet, Phys. Rev. Lett. 125, 263402 (2020).

[3] T. L. Yang, P. Grišins, Y. T. Chang, Z. H. Zhao, C. Y. Shih, T. Giamarchi, and R. G. Hulet, Phys. Rev. Lett. 121, 103001 (2018).