  Direct detection experiments turn to lose sensitivity of searching for a
sub-MeV light dark matter candidate due to the threshold of recoil energy.
However, such light dark matter particles can be accelerated by energetic
cosmic-rays such that they can be detected with existing detectors. We derive
the constraints on the scattering of a boosted light dark matter and electron
from the XENON100/1T experiment. We illustrate that the energy dependence of
the cross section plays a crucial role in improving both the detection
sensitivity and also the complementarity of direct detection and other
experiments.
