Resonant excitations of a Bose Einstein condensate in an optical lattice

TL;DR

This paper experimentally explores how a Bose-Einstein condensate in a 1D optical lattice responds to phase and amplitude modulations resonant with its band structure, revealing interaction-sensitive and immune excitation lines.

Contribution

It provides new experimental insights into resonant excitations in BECs within optical lattices, highlighting the effects of interactions and external confinement on phonon transitions.

Findings

Identification of interaction-sensitive and immune excitation lines

Good agreement between experimental results and numerical simulations

Direct measurement of n-phonon transition populations via band mapping

Abstract

We investigate experimentally a Bose Einstein condensate placed in a 1D optical lattice whose phase or amplitude is modulated in a frequency range resonant with the first bands of the band structure. We study the combined effect of the strength of interactions and external confinement on the 1 and 2-phonon transitions. We identify lines immune or sensitive to atom-atom interactions. Experimental results are in good agreement with numerical simulations. Using the band mapping technique, we get a direct access to the populations that have undergone $n$-phonon transitions for each modulation frequency.