Phonons in a nanoparticle mechanically coupled to a substrate

2019-12-23 16:05:43

low substrate phonon nanoparticle vibrational

责任者: Patton, K.R.;Geller, M.R. 单位: Dept. of Phys. & Astron., Univ. of Georgia, Athens, GA, USA 来源出处: Physical Review B (Condensed Matter and Materials Physics)(Phys. Rev., B, Condens, Matter Mater. Phys. (USA)),2003/04/15,67(15):155418-1 摘要: The discrete nature of the vibrational modes of an isolated nanometer-scale solid dramatically modifies its low-energy electron and phonon dynamics from that of a bulk crystal. However, nanocrystals are usually coupled-even if only weakly so-to an environment consisting of other nanocrystals, a support matrix, or a solid substrate, and this environmental interaction will modify the vibrational properties at low frequencies. In this paper we investigate the modification of the vibrational modes of a spherical insulating nanoparticle caused by a weak mechanical coupling to a semi-infinite substrate. The phonons of the bulk substrate act as a bath of harmonic oscillators, and the coupling to this reservoir shifts and broadens the nanoparticles modes. The vibrational density of states in the nanoparticle is obtained by solving the Dyson equation for the phonon propagator, and we show that environmental interaction is especially important at low frequencies. As a probe of the modified phonon spectrum, we consider nonradiative energy relaxation of a localized electronic impurity state in the nanoparticle, for which good agreement with a recent experiment is found 关键词: impurity states;nanoparticles;nonradiative transitions;phonon spectra;phonons;nanoparticles;mechanical coupling;vibrational mode modification;semi-infinite substrate;harmonic oscillators;vibrational density of states;Dyson equation;phonon propagator;low frequencies;modified phonon spectrum;nonradiative energy relaxation;localized electronic impurity state