Chiral topological superconductivity in hole-doped Sn/Si(111)

TL;DR

This paper combines experimental data and advanced theoretical methods to demonstrate that hole-doped Sn/Si(111) exhibits chiral topological superconductivity with a $d$-wave order parameter and a Chern number of 4, with charge density wave as a competing phase.

Contribution

It provides a comprehensive theoretical analysis confirming the chiral $d$-wave superconductivity and topological nature of Sn/Si(111) using ab initio, renormalization group, and Bogoliubov-de Gennes methods.

Findings

Superconductivity in Sn/Si(111) is chiral $d$-wave with Chern number 4.

Excellent agreement between experimental and theoretical quasi-particle interference data.

Charge density wave order competes with superconductivity, magnetically ordered phases are absent.

Abstract

A third monolayer of tin atoms on the semiconductor substrate Si(111) has been shown to become superconducting upon six to ten percent hole doping. Experiments have reported promising results hinting at a superconducting chiral $d$-wave order parameter. Here we examine Sn/Si(111) by combining most recent ab initio results, quasi-particle interference calculations, state-of-the-art truncated-unity functional renormalization group simulations and Bogoliubov-de Gennes analysis. We show remarkable agreement between experimental and theoretical quasi-particle interference data both in the metallic and superconducting regimes. The interacting phase diagram reveals that the superconductivity is indeed chiral $d$-wave with Chern number $C=4$. Surprisingly, magnetically ordered phases are absent, instead we find charge density wave order, as observed in related compounds, as a competing phase. Our results demonstrate that Sn/Si(111) is an outstanding candidate material for chiral topological superconductivity.