Suchergebnisse

Topological insulators (TIs) with an inverted bulk band and a strong spin-orbit coupling exhibit gapless topological surface states (TSSs) protected by time-reversal symmetry. Helical spin textures driven by spin-momentum locking offer the opportunity to generate spin-polarized currents and therefore TIs are expected to be used for future spintronic applications. For practical applications TIs are urgently required that are operable at room temperature due to a wide bulk band gap as well as a distinct topological surface state that is robust to atmospheric exposure. Here we show two distinguishable TSSs originating from different terminations on PbBi4Te4S3 by using spin- and angle-resolved photoemission spectroscopy. We find that one TSS is persistently observed, while the other becomes invisible upon intentional oxygen exposure. The result signifies the presence of a protected TSS buried under the topmost surface. Our finding paves the way for realizing a topological spintronics device under atmospheric conditions. ; This work was partly supported by the bilateral collaboration program between RFBR (Russia; No. 15-52-50017) and JSPS (Japan) and also by KAKENHI Grants No. 17H06138 and No. 18H03683. K.S. was financially supported by a Grant-in-Aid for JSPS Fellows (No. 16J03874). The study has also been supported by the Russian Science Foundation (Grant No. 17-12-01047) and RFBR (Grant No. 17-08-00955) for growing the single crystals and characterizing the samples. I.V.S. acknowledges financial support from the Russian Science Foundation (Grant No. 18-12-00169) for band structure calculations and the Ministry of Education and Science of the Russian Federation within governmental program Megagrants (State Task No. 3.9003.2017/9.10) for charge density calculations. This work has been partly performed in the framework of the nanoscience foundry and fine analysis (NFFA-MIUR Italy, Progetti Internazionali) facility. E.V.C. acknowledges financial support from the Saint Petersburg State University Project No. 15.61.202.2015 and the Spanish Ministry of Science and Innovation Grant No. FIS2016-75862-P. ; Peer reviewed