Fig. 4: Illustration of experimental configuration and momentum-lattice encoding scheme.
From: Engineering topological chiral transport in a flat-band lattice of ultracold atoms
a The momentum lattice is constructed with three Raman-Bragg laser pairs, which are indicated with different colors and labeled by their corresponding frequencies \(\{{\omega }_{j}^{+},{\omega }_{j,p}^{-}\}\) (j = 1, 2, 3). b Configuration for the multi-frequency Raman-Bragg couplings. The solid (dashed) lines represent the single-frequency (multi-frequency) lasers. The sites An and Bn (Cn) are encoded with the momentum states of hyperfine level F = 1 (F = 2). As shown in the figure, the pairs of momentum states \(\{\left\vert n,a\right\rangle ,\left\vert n,b\right\rangle \}\) and \(\{\left\vert n,b\right\rangle ,\left\vert n+1,a\right\rangle \}\) are all coupled with laser pairs \(\{{\omega }_{1}^{+},{\omega }_{1,p}^{-}\}\), while the corresponding momentum states \(\{\left\vert n,a\right\rangle ,\left\vert n,c\right\rangle \}\), and \(\{\left\vert n,c\right\rangle ,\left\vert n+1,a\right\rangle \}\) are coupled with laser pairs \(\{{\omega }_{2}^{+},{\omega }_{2,p}^{-}\}\) and \(\{{\omega }_{3}^{+},{\omega }_{3,p}^{-}\}\), respectively. The frequencies \({\omega }_{j,p}^{-}\) are tuned to satisfy the two-photon resonant condition. The single-photon detuning is around 2.8 GHz. The hyperfine split between levels F = 1 and F = 2 of 87Rb is about 6.8 GHz
