  The dynamics of excitons in a one-dimensional ensemble with partial spatial
order are studied. During optical excitation, cold Rydberg atoms spontaneously
organize into regular spatial arrangements due to their mutual interactions.
This emergent lattice is used as the starting point to study resonant energy
transfer triggered by driving a $nS$ to $n^\prime P$ transition using a
microwave field. The dynamics are probed by detecting the survival probability
of atoms in the $nS$ Rydberg state. Experimental data qualitatively agree with
our theoretical predictions including the mapping onto XXZ spin model in the
strong-driving limit. Our results suggest that emergent Rydberg lattices
provide an ideal platform to study coherent energy transfer in structured media
without the need for externally imposed potentials.
