*

2D materials research is one of the hot topics in condensed-matter science, but most studies are performed on nanometer-thick crystals fabricated either by mechanical exfoliation or by CVD. On the other hand, the bottom-up approach by MBE is very much limited despite its many advantages from materials science viewpoint, for example, availability of a large-area sample, potential creation of novel quantum 2D materials even including hardly-cleavable and thermodynamically-metastable compounds, as well as scalability to a variety of heterostructures. In this presentation, we will report MBE growth of 3R-Ta_1+xSe₂, a thermodynamically-metastable polar superconductor, and its superconducting properties, which turned out to be very much different from those of thermodynamically-stable 2H-TaSe₂ in terms of T_c and superconducting anisotropy [1]. [1] Y. Tanaka et al., Nano Lett. 20, 1725 (2020).