Dominant scattering channel induced by two-body collision of D -band atoms in a triangular optical lattice

Abstract

The mechanism of atomic collisions in excited bands plays an important role in both the atomic dynamics in high bands of optical lattices and the simulation of condensed matter physics. Atoms distributed in an excited band of an optical lattice can collide and decay to other bands through different scattering channels. In the excited bands of a one-dimensional lattice there is no significant difference between the cross sections to different scattering channels, due to the sameness of all of the geometrical couplings. Here, we investigate the collisional scattering channels for atoms in the excited bands of a triangular optical lattice and demonstrate a dominant scattering channel in the experiment. A shortcut method is utilized to load Bose-Einstein condensate of $^{87}\mathrm{Rb}$ atoms into the $\mathrm{\ensuremath{\Gamma}}$ point of the first $D$ band with zero quasimomentum in the triangular optical lattice. After some evolution time, the number of atoms scattering into the $S$ band induced by two-body collisions is around four times the number that scatter into the second most populated band. Our numerical calculation shows that the $ss$ scattering channel is dominant, which is roughly consistent with the experimental measurement. The appearance of dominant scattering channels in a triangular optical lattice is owing to nonorthogonal lattice vectors. This work is helpful for the research on many-body systems and directional enhancement in optical lattices.