Wigger Daniel, Karakhanyan Vage, Schneider Christian, Kamp Martin, Höfling Sven, Machnikowski Paweł, Kuhn Tilmann, Kasprzak Jacek
Opt Lett. 2020 Feb 15;45(4):919-922. doi: 10.1364/OL.385602.
When an electron-hole pair is optically excited in a semiconductor quantum dot, the host crystal lattice adapts to the presence of the generated charge distribution. Therefore, the coupled exciton-phonon system has to establish a new equilibrium, which is reached in the form of a quasiparticle called a polaron. Especially, when the exciton is abruptly generated on a timescale faster than the typical lattice dynamics, the lattice cannot follow adiabatically. Consequently, rich dynamics on the picosecond timescale of the coupled system is expected. In this study, we combine simulations and measurements of the ultrafast, coherent, nonlinear optical response, obtained by four-wave mixing (FWM) spectroscopy, to resolve the formation of this polaron. By detecting and investigating the phonon sidebands in the FWM spectra for varying pulse delays and different temperatures, we have access to the influence of phonon emission and absorption processes, which finally result in the emission of an acoustic wave packet.
当在半导体量子点中光激发一个电子-空穴对时，主体晶格会适应所产生的电荷分布的存在。因此，耦合的激子-声子系统必须建立一个新的平衡，这个平衡以一种称为极化子的准粒子形式达成。特别是，当激子在比典型晶格动力学更快的时间尺度上突然产生时，晶格无法绝热地跟随。因此，预计在耦合系统的皮秒时间尺度上会有丰富的动力学行为。在这项研究中，我们结合了通过四波混频（FWM）光谱获得的超快、相干、非线性光学响应的模拟和测量，以解析这种极化子的形成。通过检测和研究不同脉冲延迟和不同温度下FWM光谱中的声子边带，我们能够了解声子发射和吸收过程的影响，这些过程最终导致一个声波包的发射。
