Momentum microscopy of Pb-intercalated graphene on SiC: charge neutrality and electronic structure of interfacial Pb

TL;DR

This study uses momentum microscopy to analyze Pb-intercalated graphene on SiC, revealing charge neutrality, interfacial metallic bands, and potential for 2D superconductivity and strong spin-orbit effects.

Contribution

It provides detailed electronic structure characterization of Pb-intercalated graphene, highlighting interfacial quantum confinement and novel band features not previously observed.

Findings

Pb-intercalated graphene is nearly charge neutral with low p-type carriers.

Distinct metallic bands related to 2D-Pb are observed at the interface.

A 10x10 Moiré superperiodicity is identified, indicating complex interfacial structure.

Abstract

Intercalation is an established technique for tailoring the electronic structure of epitaxial graphene. Moreover, it enables the synthesis of otherwise unstable two-dimensional (2D) layers of elements with unique physical properties compared to their bulk versions due to interfacial quantum confinement. In this work, we present uniformly Pb-intercalated quasi-freestanding monolayer graphene on SiC, which turns out to be essentially charge neutral with an unprecedented $p$-type carrier density of only $(5.5\pm2.5)\times10^9$ cm$^{-2}$. Probing the low-energy electronic structure throughout the entire first surface Brillouin zone by means of momentum microscopy, we clearly discern additional bands related to metallic 2D-Pb at the interface. Low-energy electron diffraction further reveals a $10\times10$ Moir\'e superperiodicity relative to graphene, counterparts of which cannot be directly identified in the available band structure data. Our experiments demonstrate 2D interlayer confinement and associated band structure formation of a heavy-element superconductor, paving the way towards strong spin-orbit coupling effects or even 2D superconductivity at the graphene/SiC interface.