  We study correlation functions of elementary fermions in strongly interacting
field theories using the AdS/CFT correspondence. This correspondence
generically associates bulk fields to composite operators in field theory. We
modify the holographic prescription in order to obtain correlators that
correspond to fermonic single-particle excitations by introducing a dynamical
fermionic source localized on a UV brane in a holographic background. We work
out the conditions when these correlators obey the zeroth frequency sum-rule
satisfied by angle-resolved photo-emission spectroscopy (ARPES) and are thus
directly relevant to the AdS/CMT correspondence. To illustrate our techniques,
we study field theories at zero chemical potential with an arbitrary dynamical
exponent z, i.e., the Lifshitz invariant conformal field theories, including
the usual relativistic case z=1.
