Soavi Giancarlo, Scotognella Francesco, Viola Daniele, Hefner Timo, Hertel Tobias, Cerullo Giulio, Lanzani Guglielmo
Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy.
1] Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy [2] IFN-CNR, Piazza L. da Vinci, 32, 20133 Milano, Italy [3] Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli, 70/3, 20133 Milano, Italy.
Sci Rep. 2015 May 11;5:9681. doi: 10.1038/srep09681.
Theory predicts peculiar features for excited-state dynamics in one dimension (1D) that are difficult to be observed experimentally. Single-walled carbon nanotubes (SWNTs) are an excellent approximation to 1D quantum confinement, due to their very high aspect ratio and low density of defects. Here we use ultrafast optical spectroscopy to probe photogenerated charge-carriers in (6,5) semiconducting SWNTs. We identify the transient energy shift of the highly polarizable S33 transition as a sensitive fingerprint of charge-carriers in SWNTs. By measuring the coherent phonon amplitude profile we obtain a precise estimate of the Stark-shift and discuss the binding energy of the S33 excitonic transition. From this, we infer that charge-carriers are formed instantaneously (<50 fs) even upon pumping the first exciton, S11. The decay of the photogenerated charge-carrier population is well described by a model for geminate recombination in 1D.
理论预测了一维（1D）中激发态动力学的独特特征，这些特征难以通过实验观察到。单壁碳纳米管（SWNTs）由于其非常高的纵横比和低密度的缺陷，是一维量子限制的极佳近似。在这里，我们使用超快光学光谱来探测（6,5）半导体单壁碳纳米管中的光生电荷载流子。我们将高度可极化的S33跃迁的瞬态能量位移识别为单壁碳纳米管中电荷载流子的敏感指纹。通过测量相干声子振幅分布，我们获得了斯塔克位移的精确估计，并讨论了S33激子跃迁的结合能。由此，我们推断即使在泵浦第一个激子S11时，电荷载流子也会瞬间形成（<50飞秒）。光生电荷载流子群体的衰减可以用一维中双生复合的模型很好地描述。
