Affiliation:
1. Vienna Center for Quantum Science and Technology
Abstract
We study the effects of strong inter-particle interaction on
diffraction of a Bose-Einstein condensate of
^6\mathrm{Li}_26Li2
molecules from a periodic potential created by pulses of a far detuned
optical standing wave. For short pulses we observe the standard
Kapitza-Dirac diffraction, with the contrast of the diffraction pattern
strongly reduced for very large interactions due to
interaction-dependent loss processes. For longer pulses diffraction
shows the characteristic for matter waves impinging on an array of tubes
and coherent channeling transport. We observe a slowing down of the time
evolution governing the population of the momentum modes caused by the
strong atom interaction. A simple physical explanation of that slowing
down is the phase shift caused by the self-interaction of the forming
matter wave patterns inside the standing light wave. Simple 1D mean
field simulations qualitatively capture the phenomenon, however to
quantitatively reproduce the experimental results the molecular
scattering length has to be multiplied by factor of 4.2. In addition,
two contributions to interaction-dependent degradation of the coherent
diffraction patterns were identified: (i) in-trap loss of molecules
during the lattice pulse, which involves dissociation of Feshbach
molecules into free atoms, as confirmed by radio-frequency spectroscopy
and (ii) collisions between different momentum modes during separation.
This was confirmed by interferometrically recombining the diffracted
momenta into the zero-momentum peak, which consequently removed the
scattering background.
Funder
Austrian Science Fund
Bundesministerium für Wissenschaft, Forschung und Wirtschaft
Deutsche Forschungsgemeinschaft
Horizon 2020
Vienna Science and Technology Fund
Subject
General Physics and Astronomy