Absence of Dirac Electrons in Silicene on Ag (111) Surfaces

TL;DR

This study uses first-principles calculations to show that silicene on Ag(111) surfaces lacks Dirac electrons due to structural buckling and orbital mixing, suggesting alternative substrates or treatments to preserve Dirac states.

Contribution

It provides detailed insights into the stability and electronic structure of silicene on Ag(111), revealing the absence of Dirac electrons and proposing alternative methods to maintain them.

Findings

Dirac electrons are absent near Fermi energy in silicene/Ag(111).

Multiple stable silicene structures exist on Ag(111).

BN substrate or hydrogen treatment may preserve Dirac electrons.

Abstract

We report first-principles calculations that clarify stability and electronic structures of silicene on Ag(111) surfaces. We find that several stable structures exist for silicene/Ag(111), exhibiting a variety of images of scanning tunneling microscopy. We also find that Dirac electrons are {\em absent} near Fermi energy in all the stable structures due to buckling of the Si monolayer and mixing between Si and Ag orbitals. We instead propose that either BN substrate or hydrogen processing of Si surface is a good candidate to preserve Dirac electrons in silicene.