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

Li, Peigen; Zhang, Jihai; Zhu, Di; Chen, Cui-Qun; Yi, Enkui; Shen, Bing; Hou, Yusheng; Yan, Zhongbo et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

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<sub>2</sub>) on a niobium diselenide (NbSe<sub>2</sub>) superconductor. Single-layer CrI<sub>2</sub> nanosheets, which hold antiferromagnetic (AFM) ground states by our first-principles calculations, were epitaxially grown on the layered NbSe<sub>2</sub> 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<sub>2</sub> nanosheets. Magnetic-flux vortices induced by an external field exhibit broken 3-fold rotational symmetry of the pristine NbSe<sub>2</sub> superconductor, implying the efficient modulation of the interfacial superconducting states by the epitaxial CrI<sub>2</sub> 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.