# Landauer Resistivity Dipole at One-Dimensional Defect Revealed via near-Field Photocurrent Nanoscopy

## TL;DR

Researchers used a high-resolution imaging technique to observe how electrical resistance behaves at a tiny graphene interface, confirming a long-standing theoretical model.

## Contribution

The study experimentally demonstrates Landauer resistivity dipoles at a one-dimensional graphene interface using near-field photocurrent imaging.

## Key findings

- Charge carrier accumulation was observed around the graphene interface due to Landauer resistivity dipoles.
- Photocurrent polarity matched the applied voltage at low doping levels but disappeared at higher densities.
- The results align with numerical calculations and validate the use of photocurrent nanoscopy for studying nanoscale resistance.

## Abstract

The fundamental question
of how to describe ohmic resistance at
the nanoscale was answered by Landauer in his seminal picture of the
Landauer resistivity dipole (LRD). While this picture is theoretically
well understood, experimental studies remain scarce due to the need
for noninvasive local probes. Here, we use the nanometer lateral resolution
of near-field photocurrent imaging to thoroughly characterize a monolayer–bilayer
graphene interface. Via systematic tuning of charge carrier density
and current flow, we detected charge carrier accumulation around this
nearly ideal one-dimensional defect due to the formation of the LRDs.
We found that, at low doping levels, the photocurrent exhibits the
same polarity as the applied source–drain voltage, reflecting
carrier concentration changes induced by the LRDs. This signature
disappears at higher charge carrier densities in agreement with the
numerical calculations performed. Photocurrent nanoscopy can thus
serve as a noninvasive technique to study local dissipation at hidden
interfaces.