Huang Shouyuan, Miotkowski Ireneusz, Chen Yong P, Xu Xianfan
School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA.
Sci Rep. 2020 Oct 7;10(1):16761. doi: 10.1038/s41598-020-73950-z.
Three-dimensional topological insulators have been demonstrated in recent years, which possess intriguing gapless, spin-polarized Dirac states with linear dispersion only on the surface. The spin polarization of the topological surface states is also locked to its momentum, which allows controlling motion of electrons using optical helicity, i.e., circularly polarized light. The electrical and thermal transport can also be significantly tuned by the helicity-control of surface state electrons. Here, we report studies of photo-thermoelectric effect of the topological surface states in BiTeSe thin films with large tunability using varied gate voltages and optical helicity. The Seebeck coefficient can be altered by more than five times compared to the case without spin injection. This deep tuning is originated from the optical helicity-induced photocurrent which is shown to be enhanced, reduced, turned off, and even inverted due to the change of the accessed band structures by electrical gating. The helicity-selected topological surface state thus has a large effect on thermoelectric transport, demonstrating great opportunities for realizing helicity control of optoelectronic and thermal devices.
近年来已证实存在三维拓扑绝缘体，其仅在表面具有引人入胜的无隙、自旋极化狄拉克态且具有线性色散。拓扑表面态的自旋极化也与其动量锁定，这使得能够利用光螺旋度（即圆偏振光）来控制电子的运动。表面态电子的螺旋度控制还可显著调节电输运和热输运。在此，我们报告了利用不同的栅极电压和光螺旋度对具有大可调性的BiTeSe薄膜中拓扑表面态的光热电效应进行的研究。与无自旋注入的情况相比，塞贝克系数可改变超过五倍。这种深度调谐源于光螺旋度诱导的光电流，由于电门控导致的能带结构变化，该光电流被证明会增强、减小、关闭甚至反转。因此，螺旋度选择的拓扑表面态对热电输运有很大影响，为实现光电器件和热器件的螺旋度控制展示了巨大机遇。
