Intervalley scattering in MoS2 imaged by two-photon photoemission with a high-harmonic probe
Intervalley scattering in MoS2 imaged by two-photon photoemission with a high-harmonic probe
复制标题
DOI：
10.1063/1.4965839
复制
发表时间：
2016-07
影响因子：
4
通讯作者：
R. Wallauer;J. Reimann;N. Armbrust;J. Gudde;U. Hofer
中科院分区：
文献类型：
--
作者：
R. Wallauer;J. Reimann;N. Armbrust;J. Gudde;U. Hofer
我们报告了通过使用高次谐波探针的时间和角度分辨双光子光电发射来直接绘制块状 MoS2 动量空间中的电子转移。为此，我们将高重复率高次谐波源与可调谐飞秒泵浦脉冲和 3D (kx,ky,E) 电子能谱仪结合在一起。我们表明，略高于 A 激子共振的光激发会立即占据 K 处的导带，然后超快转移（<50 fs）到 Σ 处的导带最小值。 K 和 Σ 处的两个信号在 400 fs 的观测周期内都不会消失。这里描述的技术能够直接访问 k 空间中的电荷转移动力学，并允许研究各种系统中依赖于激发的过剩能量或螺旋性的衰减时间和衰减通道。
We report on the direct mapping of electron transfer in the momentum space of bulk MoS2 by means of time- and angle-resolved two-photon photoemission with a high-harmonic probe. For this purpose, we have combined a high-repetition rate high-harmonic source with tunable femtosecond pump pulses and a 3D ( kx,ky,E) electron spectrometer. We show that optical excitation slightly above the A exciton resonance results in an immediate occupation of the conduction band at K¯ followed by an ultrafast transfer ( <50 fs) to the conduction band minimum at Σ¯. Both signals, at K¯ and Σ¯, do not vanish over the observed period of 400 fs. The technique described here enables direct access to the charge transfer dynamics in k-space and allows the study of decay times and decay channels in various systems with dependence on the excess energy or helicity of the excitation.