Anisotropic excitons and their contributions to shift current transients in bulk GaAs
Anisotropic excitons and their contributions to shift current transients in bulk GaAs
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DOI：
10.1103/physrevb.96.205201
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发表时间：
2017-11-02
影响因子：
3.7
通讯作者：
Meier, Torsten
中科院分区：
文献类型：
--
作者：
Podzimski, Reinold;Huynh Thanh Duc;Meier, Torsten
通过从频带结构的14频段K.P模型获得的基础，通过半导体Bloch方程的数值解决方案获得了散发瞬变的瞬时瞬变。这种方法提供了在带间，贴边和内标激励方面对光学引起的激发的透明描述，这些激发能够在对偏移瞬变的不同贡献之间明确区分，并完全包括共振剂以及异位的过程。在我们的数值溶液中，使用互惠空间中的地球网格，我们能够将电子孔库仑吸引力与各向异性三维带结构结合使用。我们获得了兴奋子吸收峰和连续吸收的增强，并证明了激发型波函数包含大量各向异性。激发兴奋子共振的光激发会产生明显强度的转移瞬变。但是，由于电子孔吸引力，移位距离小于频段间隙激发。因此，我们证明我们的方法能够在原子量表上提供有关超快电子动力学的重要信息。
Shift-current transients are obtained for near-band-gap excitation of bulk GaAs by numerical solutions of the semiconductor Bloch equations in a basis obtained from a 14-band k.p model of the band structure. This approach provides a transparent description of the optically induced excitations in terms of interband, intersubband, and intraband excitations which enables a clear distinction between different contributions to the shift-current transients and fully includes resonant as well as off-resonant processes. Using a geodesic grid in reciprocal space in our numerical solutions, we are able to include the electron-hole Coulomb attraction in combination with our anisotropic three-dimensional band structure. We obtain an excitonic absorption peak and an enhancement of the continuum absorption and demonstrate that the excitonic wave function contains a significant amount of anisotropy. Optical excitation at the excitonic resonance generates shift-current transients of significant strength; however, due to the electron-hole attraction the shift distance is smaller than for above-band-gap excitation. We thus demonstrate that our approach is able to provide important information on the ultrafast electron dynamics on the atomic scale.