Quasi-1D Spin-imbalance Fermi gas and a new Li quantum gas machine

Quantum simulation of ultracold atomic Fermi gases provides an ideal platform to study the behavior of electrons in solid-state systems. One particular interest is the study of the finite momentum Cooper pair, also known as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. The FFLO phase is believed to occupy larger phase space in low dimensions, whereas it is more robust against quantum and thermal fluctuations in high dimensions [1][2]. Therefore, our spin-polarized gas is prepared in the quasi-1d regime by tuning the inter-tube tunneling rate of a 2D optical lattice and the interaction strength via a magnetic Feshbach resonance. In this poster, we review our methods and progress toward the direct observation of the domain walls, where the periodicity of the domain walls is a consequence of an LO-type order parameters and finite momentum pairing.

We also present the design of a new all-optical Li Fermi gas machine as an upgraded workhorse for searching for the FFLO state with a higher image resolution and optical Fourier transformation to detect the periodic domain walls. Furthermore, we will implement Bragg spectroscopy to detect the paired and unpaired sound velocities as an additional probe for the FFLO-like phase [3]. This new apparatus also features a higher numerical aperture for our future 3D optical lattice experiment.