Molecular Vibration Induced Plasmon Decay

Noble metal nanoparticles, when interacting with an external electric field, give rise to a phenomenon called surface plasmon resonance characterized by collective valence electron oscillations, and because of this unique feature, these systems are employed for a large and heterogeneous number of applications. To improve their performance, it is necessary to develop a deep knowledge of the main factors affecting the plasmon lifetime. In order to answer this question, in this work a linear silver chain is investigated as a simplified model for silver nanorods. Through a nonadiabatic molecular dynamics approach the role of nuclear dynamics on transverse plasmon lifetime is investigated. A strong dependence of plasmon dynamics on the specific nature of nuclear motions is found: nuclear motions along the chain do not affect the transverse plasmon lifetime while motions causing a deviation from linearity of the wire have an important impact on the plasmon dynamics causing its decay. As the vibrational energy increases, the decay becomes faster because of an accelerated loss of symmetry and shows a weak Landau-like mechanism. The unveiled molecular nature of the plasmon decay on a linear wire can be representative of possible decay mechanisms taking place in larger systems. These results improve the knowledge of plasmon dynamics and can be helpful for an efficient design of more performing materials.