Fig. 2: Thermal-to-BEC phase transition in optical lattices observed via high-resolution density profiles.
From: Quantum gas magnifier for sub-lattice-resolved imaging of 3D quantum systems
a, b, Spatial density distributions of BECs in triangular optical lattices prepared at different temperatures and atom numbers of 171(1) nK and 37,000(400) atoms (a), and 310(1) nK and 106,000(600) atoms (b). The densities are shown as atom numbers per lattice site from integration over the Wigner–Seitz cells. c, d, Atom number per tube as a function of the radial position corresponding to a and b, respectively, with a bimodal fit (orange line) consisting of the condensed part (yellow line) and the thermal part (purple line). e, f, Condensate fraction (circles) obtained from the bimodal fits as a function of the temperature (e) and of the temperature in units of the scaling temperature \({T}_{{\rm{c}}}^{0}\) (f). Most error bars are smaller than the symbol size. The light-blue line in f shows the power law approximation of the non-interacting theory described in the main text. The purple line is a fit to the data with the same power law. The bandwidth of the lowest band is kB × 5.4 nK and the gap between the first and second band is kB × 290 nK. The colour encodes the total atom number of the clouds. All error bars correspond to the 68% confidence interval.
