Low energy excitations in 1D Fermi gases

We explore low-energy excitations of one-dimensional (1D) spin-½ Fermi gases confined to 2D optical lattices. The quasi-1D tubes are prepared with a pseudo-spin-1/2 system consisting of the lowest and third-to-lowest hyperfine sublevels of ⁶Li. Known to host several exotic phases, fermions in 1D provide excellent testbeds to simulate exactly solvable models. Previously, we have reported the observation of spin-charge separation along with signatures of a non-linear Luttinger liquid [1], spin-incoherent Tomonaga Luttinger liquid (TLL) [2], as well as the signatures of the Luther Emery phase where the spin-charge separation is inverted compared to the repulsive TLL case [3]. Imposing a standing wave along the 1D tubes explored in previous works allows us to simulate a new class of model- the 1D Fermi Hubbard (FH) model. In this work, we study the low-energy excitations of the 1D FH model using Bragg spectroscopy. By choosing the detuning of the Bragg beams, we can excite the spin and charge density waves independently.

[1] Senaratne, R., Cavazos-Cavazos, D., Wang, S., He, F., Chang, Y. T., Kafle, A., ... & Hulet, R. G. (2022). Spin-charge separation in a one-dimensional Fermi gas with tunable interactions. Science, 376(6599), 1305-1308.

[2] Cavazos-Cavazos, D., Senaratne, R., Kafle, A., & Hulet, R. G. (2023). Thermal disruption of a Luttinger liquid. Nature Communications, 14(1), 3154.

[3] Kafle, A., Senaratne, R., Cavazos-Cavazos, D., Giamarchi, T., Pu, H., Guan, X-W. & Hulet, R.G (2024). Bragg spectroscopy of a 1D Fermi gas with attractive interactions. (in preparation)