Interplay of crystal symmetry, strong spin−orbit coupling (SOC), and many-body interactions in low dimensional materials provides a fertile ground for the discovery of unconventional electronic and magnetic properties and versatile functionalities. Two-dimensional (2D) allotropes of group 15 elements are appealing due to their structures and controllability over symmetries and topology under strong SOC. Here, we report the heteroepitaxial growth of a proximity-induced superconducting 2D square-lattice bismuth monolayer on superconducting Pb films. The square lattice of monolayer bismuth films in a C4 symmetry together with a stripey moir\'e structure is clearly resolved by our scanning tunneling microscopy and its atomic structure is revealed by density functional theory (DFT) calculations. A Rashba-type spin-split Dirac band is predicted by DFT calculations to exist at the Fermi level and becomes superconducting through the proximity effect from the Pb substrate. We suggest the possibility of a topological superconducting state in this system with magnetic dopants/field. This work introduces an intriguing material platform with 2D Dirac bands, strong SOC, topological superconductivity, and the moir\'e superstructure.
@article{arxiv.2304.02243,
title = {Realizing a Superconducting Square-Lattice Bismuth Monolayer},
author = {Eunseok Oh and Kyung-Hwan Jin and Han Woong Yeom},
journal= {arXiv preprint arXiv:2304.02243},
year = {2023}
}