Visualizing topological edge states of single and double bilayer Bi supported on multibilayer Bi(111) films

Physical Review B 98, 245108 (2018)

Visualizing topological edge states of single and double bilayer Bi supported on multibilayer Bi(111) films

Lang Peng, Jing-Jing Xian, Peizhe Tang, Angel Rubio, Shou-Cheng Zhang, Wenhao Zhang,, Ying-Shuang Fu

Freestanding single bilayer Bi(111) is a two-dimensional topological insulator with edge states propagating along its perimeter. Given the interlayer coupling experimentally, the topological nature of Bi(111) thin films and the impact of the supporting substrate on the topmost Bi bilayer are still under debate. Here, combined with scanning tunneling microscopy and first-principles calculations, we systematically study the electronic properties of Bi(111) thin films grown on a NbSe2 substrate. Two types of nonmagnetic edge structures, i.e., a conventional zigzag edge and a 2 × 1 reconstructed edge, coexist alternately at the boundaries of single bilayer islands, the topological edge states of which exhibit remarkably different energy and spatial distributions. Prominent edge states are persistently visualized at the edges of both single and double bilayer Bi islands, regardless of the underlying thickness of Bi(111) thin films. We provide an explanation for the topological origin of the observed edge states that is verified with first-principles calculations. Our paper clarifies the long-standing controversy regarding the topology of Bi(111) thin films and reveals the tunability of topological edge states via edge modifications.

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This work is funded by the National Key Research and Development Program of China (Grants No. 2017YFA0403501, No. 2016YFA0401003, and No. 2018YFA0307000), the National Science Foundation of China (Grants No. 11774105,No. 11504056, No. 11522431, and No. 11474112), and the Fundamental Research Funds for the Central Universities (Grant No. 2017KFXKJC009). P.Z.T and S.-C.Z acknowledge the Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515. A.R. acknowledges financial support from the European Research Council (Grant No. ERC-2015-AdG-694097) and European Union’s H2020 program under Grant No. 676580 (NOMAD). The project leading to this application has received funding from the European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska-Curie Grant No. 793609.

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