  Atoms excited into high-lying Rydberg states and under strong dipole-dipole
interactions exhibit phenomena associated with highly correlated and complex
systems. We perform first principles numerical simulations on the dynamics of
such systems. The emergence of a roton minimum in the excitation spectrum, as
expected in strongly correlated gases and accurately described by Feynman's
theory of liquid helium, is shown to significantly inhibit particle transport,
with a strong suppression of the diffusion coefficient, due to the emerging
spatial order. We also demonstrate how the ability to temporally tune the
interaction strength among Rydberg atoms can be used in order to overcome the
effects of disorder induced heating, allowing the study of unprecedented highly
coupled regimes.
