Adsorption of one-third monolayer of Sn on an atomically-clean Si(111) substrate produces a two-dimensional triangular adatom lattice with one unpaired electron per site. This dilute adatom reconstruction is an antiferromagnetic Mott insulator; however, the system can be modulation-doped and metallized using heavily-doped p-type Si(111) substrates. Here, we show that the hole-doped dilute adatom layer on a degenerately doped p-type Si(111) wafer is superconducting with a critical temperature of 4.7 +- 0.3 K. While a phonon-mediated coupling scenario would be consistent with the observed TC, Mott correlations in the Sn-derived dangling-bond surface state could suppress the s-wave pairing channel. The latter suggests that the superconductivity in this triangular adatom lattice may be unconventional.
@article{arxiv.1912.03242,
title = {Superconductivity in a hole-doped Mott-insulating triangular adatom layer on a silicon surface},
author = {Xuefeng Wu and Fangfei Ming and Tyler S. Smith and Guowei Liu and Fei Ye and Kedong Wang and Steven Johnston and Hanno H. Weitering},
journal= {arXiv preprint arXiv:1912.03242},
year = {2020}
}