论文标题
激发波长依赖于表面和大部分三维拓扑绝缘子的超快THz发射
Excitation wavelength-dependent ultrafast THz emission from surface and bulk of three-dimensional topological insulators
论文作者
论文摘要
三维拓扑绝缘子具有各种有趣的特性，这些特性对于各种现代应用，包括在最近新兴的超快THZ光子学和Spintronics的领域。它们的无间隙摩托杆锁的拓扑表面状态具有手性自旋结构的存在与光对光敏感的THZ发射器和检测器的发展有关。在本文中，我们报告了三维拓扑绝缘子的飞秒激发脉冲波长和螺旋依赖性响应，以增强宽带THZ脉冲发射。具体而言，激发波长在近距离紫外线到近红外的范围内发生了变化，并且已经研究了BI2TE3和BI2SE3单晶的两个模型系统。据观察，在较短的波长处的光激发可以增强表面和散装状态的THZ发射。主要是，圆形光藻素效应负责表面贡献，而大体的显着贡献来自光子拖拉效应。 THZ发射的波长依赖性是通过准确地计算材料内THZ辐射的游离载体吸收的。
Three-dimensional topological insulators possess various interesting properties that are promising for various modern applications, including in the recently emerging fields of ultrafast THz photonics and spintronics. Their gapless spin-momentum-locked topological surface states with the presence of chiral spin structure are relevant for the development of light helicity-sensitive THz emitters and detectors. In this paper, we report femtosecond excitation pulse wavelength and helicity-dependent response of the three-dimensional topological insulators for an enhanced broadband THz pulse emission. Specifically, the excitation wavelength has been varied in a large range from near UV to near IR and two model systems of Bi2Te3 and Bi2Se3 single crystals have been studied. It was observed that the photoexcitation at shorter wavelengths enhances the THz emission from both the surface and bulk states. Primarily, circular photogalvanic effect is responsible for the surface contribution, while the prominent contribution in the bulk is from photon-drag effect. The wavelength-dependence of the THz emission is explained by accounting for the free carrier absorption of THz radiation within the material accurately.
