Investigation Of Circular Photogalvanic Effect In Semiconductor Two-Dimensional Electron Gas And Three-Dimensional Topological Insulators

The spin photocurrent is a spin-polarized photocurrent generated by excitation of a circularly polarized light or a linearly polarized light,including the circular photogalvanic effect current and the photoinduced inverse spin Hall current.Circular photogalvanic effect current is a useful method to investigate the spin-orbit coupling of materials,and photoinduced inverse spin Hall current is a powerful tool to study the spin Hall effect of materials.In this paper,we investigate the circular photogalvanic effect induced by the interband and intersubband excitation in semiconductor two-dimensional electrons,and the photoinduced inverse spin Hall current in three-dimensional topological insulator is also studied.The main results are as follows:1.We investigated the temperature dependence of the circular polarized photogalvanic effects in the GaAs/AlGaAs two-dimensional electron gas induced by interband and intersubband excitation.It is revealed that the Rashba-type and the Dresselhaus-type circular photogalvanic effects induced by the intersubband excitation almost increases with increasing temperature,while that induced by interband excitation nearly decreases with increasing temperatures.A model of the temperature denpendence of the electron concentration in the triangle trap with the different excitation wavelength has been developed to explain this experimental phenomenon.The interband excitation causes the electron concentration to decrease with increasing temperature,while the intersubband excitation causes the electron concentration to increase with the increasing temperature.These lead to the difference temperature dependence of circular polarized photogalvanic effects between interband and intersubband excitation.2.We investigated the inverse spin Hall effect current in the three-dimensional topological insulator Bi2Se3.Meanwhile,a model is proposed to separate the inverse spin Hall effect current of the topological surface states from that of the two-dimensional electron gas.It is revealed that the top surface states and two-dimensional electron gas at the surface of Bi2Se3 exhibit opposite signs in inverse spin Hall effect,which can be attributed to their opposite signs of the effective spin orbit coupling.We measure the inverse spin Hall effect current when the optical power varies from 100 mW to 300 mW and the temperature varies from 77 K to 300 K.The experimental results are in good agreement with the calculation results of the model,which confirms our model.Furthermore,the temperature dependence of inverse spin Hall effect current in two dimensional gas reveals that the inverse spin Hall current in the two-dimensional electron gas mainly originates from the external mechanism.3.We investigated the inverse spin Hall effect current induced by the linear polarized light and the anomalous linear photogalvanic effect current in the three-dimensional topological insulator Bi2Se3.In this paper,we propose a method to separate the linear photogalvanic effect current,the anomalous linear photogalvanic effect current and the inverse spin Hall effect current excited by the linearly polarized light in the Bi2Se3,and we measure the temperature dependence of the above signal.Meanwhile,a model has been proposed to explain the photoinduced inverse spin Hall effect current induced by linearly polarized light.Furthermore,the temperature dependence of photoinduced momentum anisotropy is obtained by measuring anomalous linear photogalvanic effect current at different temperatures.