Orbital Many-Body Dynamics of Bosons in the Second Bloch Band of an Optical Lattice

We explore Josephson-like dynamics of a Bose-Einstein condensate of rubidium atoms in the second Bloch band of an optical square lattice providing a double well structure with two inequivalent, degenerate energy minima. This oscillation is a direct signature of the orbital changing collisions predicted to arise in this system in addition to the conventional on-site collisions. The observed oscillation frequency scales with the relative strength of these collisional interactions, which can be readily tuned via a distortion of the unit cell. The observations are compared to a quantum model of two single-particle modes and to a semiclassical multiband tight-binding simulation of 12 x 12 tubular sites of the lattice. Both models reproduce the observed oscillatory dynamics and show the correct dependence of the oscillation frequency on the ratio between the strengths of the on-site and orbital changing collision processes.

Automated summary

The study investigated the Josephson-like dynamics of a Bose-Einstein condensate of rubidium atoms in an optical square lattice and found that the oscillation frequency scales with the relative strength of collisions. Comparisons between two models demonstrated that the observed oscillatory dynamics can be explained by the ratio of the strengths of these collision processes.