EAPSI: Investigating the Electronic Properties of Topological Insulator in the Presence of Magnetic Impurities

拓扑绝缘体是量子物质的一种新形态。它是独一无二的，因为它们有绝缘的体积以及导电的边缘。无论这些边的长度如何，它们都能无损地传输能量和信息。这些性质非常稳定，改变它们的唯一方法是引入磁性杂质。本项目将制造一个可调系统，可以从金属边缘状态改变为绝缘边缘结构。该研究将与韩国浦项科技大学（Pohang University of Science and Technology）教授黄延汉（wong Yeom Han）的团队合作进行。浦项科技大学是世界上为数不多的能够制造和表征二维拓扑绝缘体的团队之一。因此，这种合作为表征和制造可调谐拓扑绝缘系统提供了独特的环境。它受到时间反转对称性的保护。这种对称性可以承受任何缺陷和破坏，除了破坏时间反转对称性的磁性杂质。因此，要真正控制拓扑绝缘体的电子特性，必须了解其在磁性杂质存在下的行为。尽管对具有磁缺陷的二维ti的理论研究已经预测，时间反转打破磁缺陷会在原本无间隙的边缘状态中打开一个间隙，但还没有实验研究报道来验证这一假设。本项目的重点是利用扫描隧道显微镜（STM）在存在近藤杂质的Bi2Te2Se上制造和表征拓扑绝缘Bi（111）双分子层。美国国家科学基金会EAPSI奖与韩国国家研究基金会合作资助。

A topological insulator (TI) is a new phase of quantum matter. TIs are unique since they have insulating bulk as well as conducting edges. These edges transmit energy and information without loss, regardless of their length. These properties are very robust and the only way to change them is by introducing magnetic impurities. This project will fabricate a tunable system that can be changed from a metallic edge state to an insulating edge structure. The research will be conducted in collaboration with Professor Woong Yeom Han's group at Pohang University of Science and Technology in South Korea, one of the few groups in the world capable of fabricating and characterizing two-dimensional topological insulators. Hence, this collaboration provides a unique environment to characterize and fabricate a tunable topological insulating system. TIs are protected by time-reversal symmetry. This symmetry can withstand any defects and damage with the exception of magnetic impurities that break time-reversal symmetry. Therefore, to truly control the electronic properties of a topological insulator, one must understand its behavior in the presence of magnetic impurities. Although theoretical studies of two-dimensional TIs with magnetic defects have predicted that time-reversal breaking magnetic defects open a gap in the otherwise gapless edge state, there has been no experimental studies reported to verify this hypothesis. This project is focused on fabricating and characterizing a topological insulating Bi(111) bilayer on Bi2Te2Se in the presence of Kondo impurities using a scanning tunneling microscope (STM). This NSF EAPSI award is funded in collaboration with the National Research Foundation of Korea.