Quantum dynamical simulation of plasmon excitations in metal nanoparticles

CRISTIÁN G. SÁNCHEZ

Cancún

Congreso; XIX International Materials Research Congress; 2010

Metallic and semiconductor nanoparticles form part of some of the most tangible present day applications of nanostructured materials. In most cases these applications are the result of their special optical properties. Nanoparticles have absorptivities several orders of magnitude larger than organic dyes and their absorption spectra can be tuned via careful control of their size and shape [1]. The physics behind metallic nanoparticle optical properties is the coherent oscillation of their conduction electrons under the influence of an oscillating electromagnetic field, the Plasmon oscillation.   In this talk I will present some results obtained from time dependent simulations of the quantum evolution of conduction electrons under the influence of applied time varying electric fields. These simulations provide a detailed picture of the excitation and relaxation processes of Plasmon oscillations in metallic nanoparticles including the influence of their atomistic structure and environment. The simulations are done via real time integration of the Liouville-von Neumann equation of motion for the reduced single electron density matrix within self consistent tight-binding models of varying complexity [2,3,4]. The use of tight binding models allows for the study of particles of realistic size while at the same time providing a quantum description of the time evolving electronic structure.   The following are some of the main results that we have obtained so far and which I will present in detail in the talk:   ·         Particle size and shape dependence of the absorption energy and plasmon lifetime. ·         Influence of adsorbates and alloying on the resonance energy and lifetime. ·         Detailed information on the field enhancement in the immediate neighbourhood of the particle.   [1] U. Kreibig and M. Volmer, Optical Properties of Metal Clusters, Springer, New York, 1995. [2] M. Elstner, D. Porezag, G. Jungnickel, J. Elsner, M. Haugk, Th. S. Suhai and G. Seifert, Phys. Rev. B: Condens. Matter Mater. Phys., 1998, 58, 7260–7268. [3] C. F. A. Negre and C. G. Sanchez, J. Chem. Phys., 2008, 129, 034710. [4] M. Belen Oviedo, Christian F. A. Negre, Cristian G. Sa´nchez, Phys. Chem. Chem. Phys., (2010), DOI: 10.1039/b926051j.