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Nano Lett. 2018 Nov 14;18(11):7176-7180. doi: 10.1021/acs.nanolett.8b03282. Epub 2018 Oct 17.

Edge States at Nematic Domain Walls in FeSe Films.

Yuan Y1, Li W1,2,3, Liu B4, Deng P1, Xu Z1, Chen X1,2, Song C1,2, Wang L1,2, He K1,2,3, Xu G4, Ma X1,2, Xue QK1,2,3.

Author information

1
State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China.
2
Collaborative Innovation Center of Quantum Matter , Beijing 100084 , China.
3
Beijing Academy of Quantum Information Sciences , Beijing 100193 , China.
4
Wuhan National High Magnetic Field Center & School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China.

Abstract

Quantum spin Hall (QSH) effect is an intriguing phenomenon arising from the helical edge states in two-dimensional topological insulators. We use molecular beam epitaxy (MBE) to prepare FeSe films with atomically sharp nematic domain boundaries, where tensile strains, nematicity suppression, and topological band inversion are simultaneously achieved. Using scanning tunneling microscopy (STM), we observe edge states at the Fermi level that spatially distribute as two distinct strips in the vicinity of the domain boundaries. At the end point of the boundaries, a bound state at the Fermi level is further observed. The topological origin of the edge states is supported by density functional theory calculations. Our findings not only demonstrate a candidate for QSH states but also provide a new pathway to realize topological superconductivity in a single-component film.

KEYWORDS:

Iron selenide; QSH; domain boundary; edge state; scanning tunneling microscopy

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