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Observation of In-Gap States in a Two-Dimensional CrI 2 /NbSe 2 Heterostructure.

Peigen LiJihai ZhangDi ZhuCui-Qun ChenEnkui YiBing ShenYusheng HouZhongbo YanDao-Xin YaoDonghui GuoDingyong Zhong
Published in: Nano letters (2024)
Low-dimensional magnetic structures coupled with superconductors are promising platforms for realizing Majorana zero modes, which have potential applications in topological quantum computing. Here, we report a two-dimensional (2D) magnetic-superconducting heterostructure consisting of single-layer chromium diiodide (CrI 2 ) on a niobium diselenide (NbSe 2 ) superconductor. Single-layer CrI 2 nanosheets, which hold antiferromagnetic (AFM) ground states by our first-principles calculations, were epitaxially grown on the layered NbSe 2 substrate. Using scanning tunneling microscopy/spectroscopy, we observed robust in-gap states spatially located at the edge of the nanosheets and defect-induced zero-energy peaks inside the CrI 2 nanosheets. Magnetic-flux vortices induced by an external field exhibit broken 3-fold rotational symmetry of the pristine NbSe 2 superconductor, implying the efficient modulation of the interfacial superconducting states by the epitaxial CrI 2 layer. A phenomenological model suggests the existence of chiral edge states in a 2D AFM-superconducting hybrid system with an even Chern number, providing a qualitatively plausible understanding for our experimental observation.
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