Brown Ana M, Sundararaman Ravishankar, Narang Prineha, Schwartzberg Adam M, Goddard William A, Atwater Harry A
Thomas J. Watson Laboratories of Applied Physics, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.
Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.
Phys Rev Lett. 2017 Feb 24;118(8):087401. doi: 10.1103/PhysRevLett.118.087401. Epub 2017 Feb 21.
Ultrafast pump-probe measurements of plasmonic nanostructures probe the nonequilibrium behavior of excited carriers, which involves several competing effects obscured in typical empirical analyses. Here we present pump-probe measurements of plasmonic nanoparticles along with a complete theoretical description based on first-principles calculations of carrier dynamics and optical response, free of any fitting parameters. We account for detailed electronic-structure effects in the density of states, excited carrier distributions, electron-phonon coupling, and dielectric functions that allow us to avoid effective electron temperature approximations. Using this calculation method, we obtain excellent quantitative agreement with spectral and temporal features in transient-absorption measurements. In both our experiments and calculations, we identify the two major contributions of the initial response with distinct signatures: short-lived highly nonthermal excited carriers and longer-lived thermalizing carriers.
对等离子体纳米结构的超快泵浦-探测测量探究了受激载流子的非平衡行为，其中涉及到在典型经验分析中被掩盖的几种竞争效应。在此，我们展示了对等离子体纳米颗粒的泵浦-探测测量，并基于载流子动力学和光学响应的第一性原理计算给出了完整的理论描述，无需任何拟合参数。我们考虑了态密度、受激载流子分布、电子-声子耦合和介电函数中的详细电子结构效应，这使我们能够避免有效电子温度近似。使用这种计算方法，我们在瞬态吸收测量的光谱和时间特征方面获得了出色的定量一致性。在我们的实验和计算中，我们都识别出了初始响应的两个主要贡献，它们具有不同的特征：寿命短的高度非热受激载流子和寿命长的热化载流子。
