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 {l_brace}[Pt(en){sub 2} ]thinsp[Pt(en ){sub 2}Cl{sub 2}]thinsp(ClO{sub 4}){sub 4}{r_brace} , where en=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. {copyright} {ital 1999} {ital The American Physical Society}