Topological insulators (TI) are a phase of matter that host unusual metallic states on their surfaces. Unlike the states that exist on the surface of conventional materials, these so-called topological surfaces states (TSS) are protected against disorder-related localization effects by time reversal symmetry through strong spin-orbit coupling. By combining transport measurements, angle-resolved photo-emission spectroscopy and scanning tunneling microscopy, we show that there exists a critical level of disorder beyond which the TI Bi2Se3 loses its ability to protect the metallic TSS and transitions to a fully insulating state. The absence of the metallic surface channels dictates that there is a change in topological character, implying that disorder can lead to a topological phase transition even without breaking the time reversal symmetry. This observation challenges the conventional notion of topologically-protected surface states, and will provoke new studies as to the fundamental nature of topological phase of matter in the presence of disorder.
@article{arxiv.1609.06305,
title = {Disorder-driven topological phase transition in Bi2Se3 films},
author = {Matthew Brahlek and Nikesh Koirala and Maryam Salehi and Jisoo Moon and Wenhan Zhang and Haoxiang Li and Xiaoqing Zhou and Myung-Geun Han and Liang Wu and Thomas Emge and Hang-Dong Lee and Can Xu and Seuk Joo Rhee and Torgny Gustafsson and N. P. Armitage and Yimei Zhu and Daniel S. Dessau and Weida Wu and Seongshik Oh},
journal= {arXiv preprint arXiv:1609.06305},
year = {2016}
}