Direct visualization of electric current induced dipoles of atomic impurities

TL;DR

This study visualizes electric current induced dipoles around atomic impurities in bilayer graphene, revealing how impurity charge polarity influences dipole direction and demonstrating control of these dipoles via local current tuning, advancing atomic-scale transport understanding.

Contribution

It provides the first direct visualization of impurity-induced current dipoles at the atomic scale and demonstrates their controllability through local current adjustments.

Findings

Dipoles align parallel or anti-parallel to local current based on impurity charge polarity.

Dipoles can be redirected by tuning local current direction.

The work confirms the carrier density modulation effect proposed by Landauer.

Abstract

Learning the electron scattering around atomic impurities is a fundamental step to fully understand the basic electronic transport properties of realistic conducting materials. Although many efforts have been made in this field for several decades, atomic scale transport around single point-like impurities has yet been achieved. Here, we report the direct visualization of the electric current induced dipoles around single atomic impurities in epitaxial bilayer graphene by multi-probe low temperature scanning tunneling potentiometry as the local current density is raised up to around 25 A/m, which is considerably higher than that in previous studies. We find the directions of these dipoles which are parallel or anti-parallel to local current are determined by the charge polarity of the impurities, revealing the direct evidence for the existence of the carrier density modulation effect proposed by Landauer in 1976. Furthermore, by $in$ $situ$ tuning local current direction with contact probes, these dipoles are redirected correspondingly. Our work paves the way to explore the electronic quantum transport phenomena at single atomic impurity level and the potential future electronics toward or beyond the end of Moore's Law.