Direct Evidence of Interaction-Induced Dirac Cones in Monolayer Silicene/Ag(111) System

TL;DR

This paper provides direct experimental evidence of interaction-induced Dirac cones in monolayer silicene grown on Ag(111), revealing a new type of Dirac fermion resulting from substrate interaction, which broadens potential applications in quantum materials.

Contribution

It demonstrates the existence of Dirac cones in silicene on Ag(111), showing they originate from substrate interaction rather than pristine silicene alone.

Findings

Six pairs of Dirac cones observed at Brillouin zone edges

Dirac cones result from silicene-Ag(111) interaction, not intrinsic to silicene

First evidence of interaction-induced Dirac fermions in silicene/Ag(111)

Abstract

Silicene, analogous to graphene, is a one-atom-thick two-dimensional crystal of silicon which is expected to share many of the remarkable properties of graphene. The buckled honeycomb structure of silicene, along with its enhanced spin-orbit coupling, endows silicene with considerable advantages over graphene in that the spin-split states in silicene are tunable with external fields. Although the low-energy Dirac cone states lie at the heart of all novel quantum phenomena in a pristine sheet of silicene, the question of whether or not these key states can survive when silicene is grown or supported on a substrate remains hotly debated. Here we report our direct observation of Dirac cones in monolayer silicene grown on a Ag(111) substrate. By performing angle-resolved photoemission measurements on silicene(3x3)/Ag(111), we reveal the presence of six pairs of Dirac cones on the edges of the first Brillouin zone of Ag(111), other than expected six Dirac cones at the K points of the primary silicene(1x1) Brillouin zone. Our result shows clearly that the unusual Dirac cone structure originates not from the pristine silicene alone but from the combined effect of silicene(3x3) and the Ag(111) substrate. This study identifies the first case of a new type of Dirac Fermion generated through the interaction of two different constituents. Our observation of Dirac cones in silicene/Ag(111) opens a new materials platform for investigating unusual quantum phenomena and novel applications based on two-dimensional silicon systems.