van der Waals heterostructures

A van der Waals (vdW) heterostructure provides an indispensable material platform in modern condensed-matter researches. There, weak interlayer bonding nature ensures formation of an atomically abrupt heterointerface beyond fundamental constraint imposed by lattice matching condition, while strong electronic coupling enables creation of an emergent electronic ground state that is missing in individual materials. The most studies on the vdW heterostructures have been made by the top-down approach, exfoliation, pick-up, and dry-transfer. On the other hand, the bottom-up approach by MBE has remained almost totally undeveloped, probably due to difficulties in fabrication of high-enough quality samples. However, MBE should enable fabrication of a few layer samples even for hardly-cleavable materials as well as thermally-metastable compounds, and therefore, the MBE-based approach should be in principle extremely powerful and important for broadening the scope of vdW heterostructures.

Here we fabricated vdW heterostructures by MBE, where a new type of 2D magnet, vanadium selenide epitaxial thin film¹, was incorporated. The result demonstrates a new type of magnetic proximity effect mediated by Zeeman spin-orbit interaction of NbSe₂ across the vdW interface, which significantly impacts the magnetic properties of a neighboring 2D ferromagnet². In the presentation, we will show transport properties of those magnetic heterostructures, and discuss the interface proximity effect on 2D magnetism.

[1] M. Nakano et al, Nano Lett. 12, 8806-8810 (2019). [2] Matsuoka, H. et al. Nano Lett. 21, 1807–1814 (2021).