Superconductivity in a hole-doped Mott-insulating triangular adatom layer on a silicon surface

TL;DR

This study demonstrates that a hole-doped, Mott-insulating triangular adatom layer on silicon exhibits superconductivity at around 4.7 K, indicating potential unconventional pairing mechanisms beyond phonon mediation.

Contribution

It reveals superconductivity in a hole-doped triangular adatom lattice on silicon, highlighting the role of Mott correlations and suggesting unconventional pairing mechanisms.

Findings

Superconductivity observed at 4.7 K in the adatom layer.

Hole doping induces a transition from Mott insulator to superconductor.

Potential unconventional pairing mechanisms suggested by Mott correlations.

Abstract

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.