  We discuss the use of atom interferometry as a tool to search for Dark Matter
(DM) composed of ultra-light scalar fields. Previous work on ultra-light DM
detection using accelerometers has considered the possibility of equivalence
principle violating effects whereby gradients in the dark matter field can
directly produce relative accelerations between media of differing composition.
In atom interferometers, we find that time-varying phase signals from
oscillatory, or dilaton-like, DM can also arise due to changes in the atom rest
mass that can occur between light-pulses throughout the interferometer sequence
as well as changes in the earth's gravitational field. We estimate that several
orders of magnitude of unexplored phase space for light DM fields can be probed
with our proposed method.

Atomic Physics;Instrumentation and Methods for Astrophysics;High Energy Physics - Phenomenology