Observation of Intrinsically Localized Modes in a Discrete Low-Dimensional Material

We report the experimental observation of intrinsic dynamically localized vibrational states in crystals of the highly nonlinear halide-bridged mixed-valence transition metal complex $\{\left[\mathrm{Pt}\right(\mathrm{en}{)}_2\left]\right[\mathrm{Pt}\left(\mathrm{en}{)}_2{\mathrm{Cl}}_2\right]({\mathrm{ClO}}_4{)}_4\}$, where $\mathrm{en}=\mathrm{ethylenediamine}$. These states are identified by the distinctive structure and strong redshifts they impose upon the overtone resonance Raman spectra. Quantitative modeling of the observed redshifts is presented based on a nonadiabatic coupled electron-lattice model that self-consistently predicts strong nonlinearity and highly localized multiquanta bound states.