Study On Terahertz Characteristics Of Multilayer Ferromagnetic Films And Topological Insulating Films

In this paper,the properties of terahertz radiation from[Pt/Co]₃/MnIr multilayers were studied.In addition,the application of time domain terahertz spectroscopy and optical pump terahertz probe technology in the photoelectric characteristics of topological insulator Bi₂Se₃ films was studied.The main results are summarized as follows:（1）First,it was found that the intensity of terahertz signal radiated by the[Pt/Co]₃/MnIr multilayers was linearly related to the power density of the femtosecond laser.Next,we can reverse the polarity of the generated terahertz signal by changing the direction of the laser incident and the direction of the applied magnetic field,respectively.The main principle and mechanism is the inverse spin Hall effect.In addition,by changing the thickness of the non-magnetic film Pt and the magnetic film Co in a certain range,it was found that the intensity of the terahertz signal changed,which decreased with the increase of the Pt thickness and increased with the increase of the Co thickness.It was also found that the interface effects such as inverse Rashba-Edelstein effect also contribute to terahertz radiation.（2）Using time domain terahertz spectroscopy,it was found that the temperature changed the transmission terahertz signal of the topological insulator Bi₂Se₃ thin film sample,and the transmission signal intensity gradually decreased as the temperature decreased from room temperature to 80K.Using 800 nm optical pump-terahertz probe technology,the conductance of the sample was studied.