  We combine constraints from linear and nonlinear scales, for the first time,
to study the interaction between dark matter and dark energy. We devise a novel
N-body simulation pipeline for cosmological models beyond $\Lambda$CDM. This
pipeline is fully self-consistent and opens a new window to study the nonlinear
structure formation in general phenomenological interacting dark energy models.
By comparing our simulation results with the SDSS galaxy-galaxy weak lensing
measurements, we are able to constrain the strength of interaction between dark
energy and dark matter. Compared with the previous studies using linear
examinations, we point to plausible improvements on the constraints of
interaction strength by using small scale information from weak lensing. This
improvement is mostly due to the sensitivity of weak lensing measurements on
nonlinear structure formation at low redshift. With this new pipeline, it is
possible to look for smoking gun signatures of dark matter-dark energy
interaction.
