  We study the electromagnetically induced transparency (EIT) effect with two
individually addressed four-level Rydberg atoms subjected to the interatomic
van der Waals interaction. We derive an effectively atomic Raman transition
model where two ladders of the usual Rydberg-EIT setting terminating at the
same upper Rydberg level of long radiative lifetime are turned into a
Rydberg-EIT lambda setup via two-photon transitions, leaving the middle levels
of each ladder largely detuned from the coupling and probe laser beams. It can
hence overcome the limits of applications for EIT with atoms of the ladder-type
level configuration involving a strongly decaying intermediate state by
inducing coherence between two ground states. By probing one of the atoms, we
observe four doublets of absorption induced by the Autler-Townes (AT) splitting
and the van der Waals interaction. In particular, we find that the location of
the EIT center remains unchanged compared to the interatomic-interaction-free
case, which demonstrated that the interference among the multiple transition
channels is basically destructive. The EIT with controlled Rydberg-Rydberg
interaction among few atoms provides a versatile tool for engineering the
propagation dynamics of light.
