磁性掺杂三维拓扑绝缘体的自旋相关光电流研究

通过圆偏振光致电流及反常圆偏振光致电流的光学实验方法,研究磁性掺杂对三维拓扑绝缘体的影响.在圆偏振光激发下,相对于未掺杂三维拓扑绝缘体Bi2 Te3,其光电流方向不变,但幅值有所减小.这是由于磁性掺杂使得三维拓扑绝缘体狄拉克能带带隙打开,相同激发条件下,带间激发概率降低,光生自旋极化载流子浓度降低.对其光电导信号的分析...

Investigation on spin dependent photocurrent of magnetically doped three-dimensional topological insulators

In this work, the circular photogalvanic effect (CPGE) and the abnormal circular photogalvanic effect (ACPGE) of the magnetically doped three-dimensional topological insulator (Cr0.03Bi0.97)2Te3 have been investigated. Compared with the undoped three-dimensional topological insulator Bi2Te3, the photocurrent direction remains unchanged, and the amplitude is reduced. Experimental analysis shows that the reason for this phenomenon is that magnetic doping makes the three-dimensional topological insulator Dirac band gap open. Under the same circularly polarized light excitation condition, the probability of inter-band excitation is reduced, and the concentration of photogenerated spin-polarized carriers is reduced. Comparing the photoconductive signals of the two, it is also found that the magnetic doping greatly reduces the absorption of excitation light by the topological insulator, thereby limiting the generation of photocurrent. In addition, the upper and lower surface states of the magnetically doped three-dimensional topological insulator contribute to the oppositely directed ACPGE, so that the total ACPGE changes sign three times with the position of the excitation light. Through fitting, we separate the respective contributions of the upper and lower surface states.