Soifer H, Gauthier A, Kemper A F, Rotundu C R, Yang S-L, Xiong H, Lu D, Hashimoto M, Kirchmann P S, Sobota J A, Shen Z-X
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA.
Phys Rev Lett. 2019 Apr 26;122(16):167401. doi: 10.1103/PhysRevLett.122.167401.
We study the microscopic origins of photocurrent generation in the topological insulator Bi_{2}Se_{3} via time- and angle-resolved photoemission spectroscopy. We image the unoccupied band structure as it evolves following a circularly polarized optical excitation and observe an asymmetric electron population in momentum space, which is the spectroscopic signature of a photocurrent. By analyzing the rise times of the population we identify which occupied and unoccupied electronic states are coupled by the optical excitation. We conclude that photocurrents can only be excited via resonant optical transitions coupling to spin-orbital textured states. Our work provides a microscopic understanding of how to control photocurrents in systems with spin-orbit coupling and broken inversion symmetry.
我们通过时间分辨和角分辨光电子能谱研究了拓扑绝缘体Bi₂Se₃中光电流产生的微观起源。我们对圆偏振光激发后演化的未占据能带结构进行成像，并在动量空间中观察到不对称的电子分布，这是光电流的光谱特征。通过分析分布的上升时间，我们确定了哪些占据和未占据的电子态通过光激发耦合。我们得出结论，光电流只能通过与自旋轨道纹理态耦合的共振光跃迁来激发。我们的工作为如何在具有自旋轨道耦合和反演对称性破缺的系统中控制光电流提供了微观理解。
