Observations of λ/4 structure in a low-loss radio-frequency-dressed optical lattice

We load a Bose-Einstein condensate into a one-dimensional (1D) optical lattice altered through the use of radio-frequency (rf) dressing. The rf resonantly couples the three levels of the 87Rb F = 1 manifold and combines with a spin-dependent “bare” optical lattice to result in adiabatic potentials of variable shape, depth, and spatial frequency content. We choose dressing parameters such that the altered lattice is stable over lifetimes exceeding tens of ms at higher depths than in previous work. We observe significant differences between the BEC momentum distributions of the dressed lattice as compared to the bare lattice, and find general agreement with a 1D band-structure calculation informed by the dressing parameters. Previous work using such lattices was limited by very shallow dressed lattices and strong Landau-Zener tunneling loss between adiabatic potentials, equivalent to failure of the adiabatic criterion. In this work we operate with significantly stronger rf coupling (increasing the avoided-crossing gap between adiabatic potentials), observing dressed lifetimes of interest for optical lattice-based analog solid-state physics.