Itinerant Ferromagnetism and $p+ip'$ Superconductivity in Doped Bilayer Silicene

TL;DR

This paper explores electronic instabilities in doped bilayer silicene, revealing a transition from ferromagnetism to triplet $p+ip'$ superconductivity near Van Hove singularities, with spin-orbit coupling favoring helical pairing.

Contribution

It uncovers the coexistence and competition of ferromagnetism and triplet superconductivity in doped bilayer silicene, highlighting the role of ferromagnetic fluctuations and spin-orbit coupling.

Findings

Ferromagnetism appears near Van Hove singularities.

Triplet $p+ip'$ superconductivity is stabilized near ferromagnetic regions.

Spin-orbit coupling favors helical $p+ip'$ pairing.

Abstract

We study the electronic instabilities of doped bilayer silicene using the random phase approximation. In contrast to the singlet $d+id'$ superconductivity at the low doping region, we find that the system is an itinerant ferromagnet in the narrow doping regions around the Van Hove singularities, and a triplet $p+ip'$ superconductor in the vicinity of these regions. Adding a weak Kane-Mele spin-orbit coupling to the system further singles out the time-reversal invariant equal-spin helical $p+ip'$ pairing as the leading instability. The triplet pairing identified here is driven by the ferromagnetic fluctuations, which become strong and enhance the superconducting critical temperature remarkably near the phase boundaries between ferromagnetism and superconductivity.