Anomalous decay and breather formation in doped alkali halides

Anomalous decay of doped alkali halides has been ascribed to breather formation in the immediate neighborhood of the impurity. New results support this connection. We report experimental data for NaBr and RbBr crystals showing anomalies in their slow emission decay. These data complete the earlier picture, confirming that the decay anomaly becomes bigger as the host-lattice-anion/cation mass ratio increases. We show the correlation between the decay anomaly and the breather formation as a function of this ratio. By simulating finite-temperature effects (which do not just involve white noise) in the lattice dynamics, we demonstrate that with increasing temperature the breather weakens, as is experimentally observed for the decay anomaly.