Magnetic excitations and lattice distortions in highly-doped (Sr$_{1-x}$La$_{x}$)$_{3}$Ir$_{2}$O$_{7}$

(Sr$_{1-x}$La$_{x}$)$_{3}$Ir$_{2}$O$_{7}$ has been shown to undergo a first-order phase transition from a localized antiferromagnetic insulating state to a correlated metal. We discuss the further characterization of these correlations by examining the excitation spectra of a highly-doped sample. These reveal evidence of a dispersive feature associated with an over-damped magnon mode, similar to the behavior of the undoped parent compound, as well as a higher energy excitation. The nature of the lattice distortion brought on by La-doping will also be discussed.