Long-time nonlinear dynamical evolution for P-band ultracold atoms in an optical lattice

We report the long-time nonlinear dynamical evolution of ultracold atomic gases in the P band of an optical lattice. A Bose-Einstein condensate is fast and efficiently loaded into the P band at zero quasimomentum with a nonadiabatic shortcut method. For the first 1.5 ms, this momentum state undergoes oscillations due to coherent superposition of different bands, which are followed by oscillations up to 60 ms of a much longer period. Our analysis shows the dephasing from the nonlinear interaction is very conducive to the long-period oscillations induced by the variable force due to the harmonic confinement.