Non-equilibrium carrier dynamics and band structure of graphene on 2D tin

TL;DR

This study investigates the ultrafast non-equilibrium carrier dynamics and interlayer interactions in graphene intercalated with 2D tin, revealing rapid charge transfer and hybridization effects through advanced spectroscopy and theoretical calculations.

Contribution

It provides the first detailed analysis of ultrafast carrier behavior and hybridization in graphene/2D tin heterostructures, highlighting new interlayer interaction phenomena.

Findings

Short-lived non-equilibrium carrier distribution in Sn-intercalated graphene

Transient increase in graphene's binding energy due to hole charging

Substantial hybridization between graphene π-bands and Sn states

Abstract

Intercalation of epitaxial graphene on SiC(0001) with Sn results in a well-ordered Sn $(1\times1)$ structure on the SiC surface with quasi-freestanding graphene on top. While the electronic properties of the individual layers have been studied in the past, emerging phenomena arising from possible inter-layer interactions between the 2D\,Sn layer and graphene remain unexplored. We use time- and angle-resolved photoemission spectroscopy to reveal a surprisingly short-lived non-equilibrium carrier distribution inside the Dirac cone of Sn-intercalated graphene. Further, we find that the graphene $\pi$-band exhibits a transient increase in binding energy that we attribute to charging of the graphene layer with holes. We interpret our results with support from density functional theory calculations of the graphene - 2D\,Sn heterostructure that reveal a substantial hybridization between the graphene $\pi$-bands and Sn states, providing a channel for efficient ultrafast charge transfer between the layers. Our results on the graphene - 2D\,Sn model system are expected to trigger similar investigations on related heterostructures obtained by intercalation of epitaxial graphene. Regarding the huge choice of materials that have been successfully intercalated in the past, we believe that the interlayer interactions revealed in the present work only represent the tip of the iceberg with many fascinating emerging phenomena to be discovered in the near future.