Edge states at nematic domain walls in FeSe films

TL;DR

This study demonstrates the existence of topologically protected edge states at nematic domain walls in FeSe films, suggesting potential for realizing quantum spin Hall states and topological superconductivity.

Contribution

It provides experimental evidence of edge states at nematic domain boundaries in FeSe films and links them to topological properties supported by theoretical calculations.

Findings

Edge states observed at nematic domain boundaries in FeSe films.

Bound states found at the endpoints of domain boundaries.

Support for topological origin through density functional theory.

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 endpoint 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.