Dynamics of Momentum Bifurcation of Li-6 Molecules in Shaking Optical Lattice

Upon applying a shaking optical lattice to a Bose-Einstein condensate of ultracold Li-6 molecules, we observe deformed bands with two minima resulting from the shaking, as has been previously observed in bosonic species. Time-of-flight measurements show momentum distributions concentrated at the expected quasi-band minima. However, during the evolution from the single minimum to the double minimum, the zone center acquires an inverted dispersion, which resembles the behavior of self-trapped solitons bound by interactions and having negative mass. The atoms remain at this point for a short period, before the momentum distribution acquires a distinct bifurcation into two separated but tight distributions. We here present how we study the process by tuning various variables (shaking time, lattice depth, momentum separation, interactions, etc) and probing techniques.