Strong in-plane scattering of acoustic graphene plasmons by surface atomic steps

Ni Zhang,Weiwei Luo,Mengxin Ren,Jiang Fan,Xinzheng Zhang,Jingjun Xu,Wei Wu,Wei Cai,Lei Wang

doi:10.1038/s41467-022-28614-z

Abstract

Acoustic graphene plasmons (AGPs) have ultrastrong field confinement and low loss, which have been applied for quantum effect exploration and ångström-thick material sensing. However, the exploration of in-plane scattering of AGPs is still lacking, although it is essential for the manipulation of ultraconfined optical fields down to atomic level. Here, by using scattering-type scanning near-field optical microscopy (s-SNOM), we show that the mid-infrared AGPs can be strongly scattered by atomic level height steps, even though the step height of the scatterer is four orders of magnitude smaller than the incident free wavelength. This effect can be attributed to larger back scattering of AGPs than that of the traditional graphene plasmons. Besides, the scattering of AGPs by individual scatterers can be controlled via electrical back gating. Our work suggests a feasible way to control confined optical fields with atomic level height nanostructures, which can be used for ultra-compacted strong light–matter interactions.

Highlights

Acoustic graphene plasmons (AGPs) have ultrastrong field confinement and low loss, which have been applied for quantum effect exploration and ångström-thick material sensing
Near-field imaging was realized by scattering-type scanning near-field optical microscopy (s-SNOM) which is based on a metallic atomic force microscopy (AFM) tip[29,30,31]
The ultra-fine height sensors can be realized based on that the scattering amplitude of AGPs depends a lot on the height

Summary

Introduction

Acoustic graphene plasmons (AGPs) have ultrastrong field confinement and low loss, which have been applied for quantum effect exploration and ångström-thick material sensing. By using scattering-type scanning near-field optical microscopy (s-SNOM), we show that the midinfrared AGPs can be strongly scattered by atomic level height steps, even though the step height of the scatterer is four orders of magnitude smaller than the incident free wavelength This effect can be attributed to larger back scattering of AGPs than that of the traditional graphene plasmons. 1234567890():,; Graphene plasmons (GPs)-electromagnetic fields coupled to charge carrier oscillations, have attracted a great deal of attention owing to their short wavelengths, strong field confinement, and electrical tunability[1,2,3,4] These unique properties make GPs potential applications for controlling electromagnetic waves on the nanometer scale[5], such as highly integrated sensitive spectroscopy[6], modulators[7], and detectors[8,9,10]. By engineering substrates vertically in atomic scale, like nano-etching or stacking layered materials, a variety of unique physical phenomena such as photonic crystal[22,23], Anderson localization[24,25], and functionalized optical devices[26,27] based on AGPs can be realized, finding potential applications including spectroscopy, sensing, and optoelectronics

Methods

Results

Conclusion