Realization of tunnel barriers for matter waves using spatial gaps

Understand

We experimentally demonstrate the trapping of a propagating Bose-Einstein Condensate in a Bragg cavity produced by an attractive optical lattice with a smooth envelope.

• As a consequence of the envelope, the band gaps become position-dependent and act as mirrors of finite and velocity-dependent reflectivity.
• We directly observe both the oscillations of the wave packet bouncing in the cavity provided by these spatial gaps and the tunneling out for narrow classes of velocity.
• Synchronization of different classes of velocity can be achieved by proper shaping of the envelope.