Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
J Chem Phys. 2013 May 7;138(17):174707. doi: 10.1063/1.4802000.
We consider the transient non-equilibrium electronic distribution that is created in a metal nanoparticle upon plasmon excitation. Following light absorption, the created plasmons decohere within a few femtoseconds, producing uncorrelated electron-hole pairs. The corresponding non-thermal electronic distribution evolves in response to the photo-exciting pulse and to subsequent relaxation processes. First, on the femtosecond timescale, the electronic subsystem relaxes to a Fermi-Dirac distribution characterized by an electronic temperature. Next, within picoseconds, thermalization with the underlying lattice phonons leads to a hot particle in internal equilibrium that subsequently equilibrates with the environment. Here we focus on the early stage of this multistep relaxation process, and on the properties of the ensuing non-equilibrium electronic distribution. We consider the form of this distribution as derived from the balance between the optical absorption and the subsequent relaxation processes, and discuss its implication for (a) heating of illuminated plasmonic particles, (b) the possibility to optically induce current in junctions, and (c) the prospect for experimental observation of such light-driven transport phenomena.
我们研究了在等离子体激元激发下金属纳米颗粒中产生的瞬态非平衡电子分布。光吸收后，产生的等离子体在几飞秒内退相干，产生不相关的电子-空穴对。相应的非热电子分布响应光激发脉冲和随后的弛豫过程而演变。首先，在飞秒时间尺度上，电子子系统弛豫到由电子温度特征化的费米-狄拉克分布。接下来，在皮秒时间内，与下面的晶格声子热化导致处于内部平衡的热粒子，随后与环境达到平衡。在这里，我们专注于这个多步弛豫过程的早期阶段，以及随后的非平衡电子分布的特性。我们考虑了从光吸收和随后的弛豫过程之间的平衡中得出的这种分布的形式，并讨论了它对（a）被照射的等离子体粒子的加热、（b）在结中诱导光电流的可能性，以及（c）观察这种光驱动输运现象的实验前景的影响。
