In-situ Formation of Superconducting FeTe/layered-MnTe heterostructures

Manganese telluride (MnTe) has garnered strong interest recently for its antiferromagnetic semiconductor properties, which are promising for applications in spintronics, data storage, and quantum computing. In this study, we discovered that the deposition of FeTe at 300oC onto zinc-blende MnTe (ZB-MnTe) via molecular beam epitaxy (MBE) results in a phase transition from ZB-MnTe to a layered MnTe (l-MnTe) phase with van der Waals (vdW) gaps, which is a previously unreported phase of MnTe. The l-MnTe phase was characterized using cross-sectional high-angle annular dark-field (HAADF) imaging, energy-dispersive X-ray spectroscopy (EDS) mapping, and X-ray photoelectron spectroscopy (XPS). The Fe/Te flux ratio during FeTe deposition was found to be critical to the phase transition, an increased Fe/Te flux ratio used for the FeTe growth leads to localized formation of layered Mn4Te3 (l-Mn4Te3), while a decreased Fe/Te flux ratio only generates a single monolayer of l-MnTe at the interface and the rest turns into a distorted ZB-MnTe (dZB-MnTe) phase. It was also found that FT-MT heterostructures grown at a lower substrate temperature of 250oC, as the Fe/Te flux ratio decreases, the ZB-MnTe layer was first transformed to dZB-MnTe and then to wurtzite MnTe (WZ-MnTe). The FeTe/l-MnTe heterostructure exhibits high-quality superconducting properties with a three-dimensional nature as demonstrated by its magneto-transport properties and there is evidence that l-MnTe seems to play a key role in inducing the observed superconductivity. Most importantly, this study reports the realization of layered structures of MnTe by an in-situ approach via chemical interactions, which might be further applied to generating unprecedented phases of materials under certain conditions.