Wang X B, Cheng L, Wu Y, Zhu D P, Wang L, Zhu Jian-Xin, Yang Hyunsoo, Chia Elbert E M
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore.
Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore.
Sci Rep. 2017 Oct 18;7(1):13486. doi: 10.1038/s41598-017-13701-9.
Three dimensional topological insulators, as a new phase of quantum matters, are characterized by an insulating gap in the bulk and a metallic state on the surface. Particularly, most of the topological insulators have narrow band gaps, and hence have promising applications in the area of terahertz optoelectronics. In this work, we experimentally demonstrate an electronically-tunable terahertz intensity modulator based on BiSbTeSe single crystal, one of the most insulating topological insulators. A relative frequency-independent modulation depth of ~62% over a wide frequency range from 0.3 to 1.4 THz has been achieved at room temperature, by applying a bias current of 100 mA. The modulation in the low current regime can be further enhanced at low temperature. We propose that the extraordinarily large modulation is a consequence of thermally-activated carrier absorption in the semiconducting bulk states. Our work provides a new application of topological insulators for terahertz technology.
三维拓扑绝缘体作为量子物质的一个新阶段，其特征在于体内存在绝缘能隙而表面为金属态。特别地，大多数拓扑绝缘体具有窄带隙，因此在太赫兹光电子学领域有着广阔的应用前景。在这项工作中，我们通过实验展示了一种基于BiSbTeSe单晶（最绝缘的拓扑绝缘体之一）的电可调太赫兹强度调制器。在室温下，通过施加100 mA的偏置电流，在0.3至1.4 THz的宽频率范围内实现了约62%的相对频率无关调制深度。在低温下，低电流 regime 中的调制可以进一步增强。我们认为这种异常大的调制是半导体体态中热激活载流子吸收的结果。我们的工作为拓扑绝缘体在太赫兹技术中的应用提供了新的途径。
