Spatially resolving density-dependent screening around a single charged atom in graphene

TL;DR

This study combines experimental STM/STS measurements and theoretical modeling to spatially resolve and tune the density-dependent screening of a single charged atom in graphene, revealing fundamental electron interaction behaviors.

Contribution

It provides the first direct visualization and control of screening length around a single impurity in graphene using combined experimental and theoretical approaches.

Findings

Screening length can be tuned with carrier density.

Visualization of density-dependent screening around a single impurity.

Insights into electron-electron interactions in relativistic graphene electrons.

Abstract

Electrons in two-dimensional graphene sheets behave as interacting chiral Dirac fermions and have unique screening properties due to their symmetry and reduced dimensionality. By using a combination of scanning tunneling spectroscopy (STM/STS) measurements and theoretical modeling we have characterized how graphene's massless charge carriers screen individual charged calcium atoms. A back-gated graphene device configuration has allowed us to directly visualize how the screening length for this system can be tuned with carrier density. Our results provide insight into electron-impurity and electron-electron interactions in a relativistic setting with important consequences for other graphene-based electronic devices.