Fig. 1: Synthesizing topological atomic trimer array with tunable interaction.
From: Observation of nonlinear edge states in an interacting atomic trimer array
a A topological trimer array is implemented in a momentum lattice, based on the laser-driven Bragg transitions between the discrete atomic momentum states pn with n ∈ {0,17}. Each unit cell in the trimer array includes three sites (a, b, c), and the unit cell index j ranges from 0 to 5. The intra- and intercell hopping rates are characterized by J and K, respectively, and can be individually controlled by addressing each Bragg transition. Atoms are prepared at two leftmost sites with equal weight and a relative phase ϕ. b Energy spectra as a function of J/K in the trimer array with open boundary condition in the noninteracting limit. The red lines represent topological edge states for J/K < 1. c Eigenmodes of topological trimer array correspond to the black dots in (b). Two in-phase (out-of-phase) peaks characterize the modes 1 and 2 (modes 3 and 4). d Illustration of the density-dependent, nonlinear energy induced by the atomic interactions. The site energy is shifted by \({E}_{{NL}}^{j,b}=-{{U|}{b}_{j}|}^{4}/2N\) with the mean-field interaction energy U and atomic population |bj|2 at site |j,b〉
