Energy transfer channels of the plasmon excitation process in STM tunnel junctions

TL;DR

This paper investigates how energy from inelastic tunneling electrons in STM junctions is distributed among various plasmonic and radiative channels, revealing dominant energy transfer to tip surface plasmons and significant quenching effects.

Contribution

It provides a detailed analysis of energy transfer channels in STM plasmon excitation, highlighting the dominant pathways and the role of quenching at the tip apex.

Findings

Most energy excites surface plasmons on the STM tip

Significant energy is lost through direct quenching at the tip apex

Energy distribution varies with frequency

Abstract

We study the decay of gap plasmons localized between a scanning tunneling microscope tip and metal substrate, excited by inelastic tunneling electrons. The overall excited energy from the tunneling electrons is divided into two categories in the form of resistive dissipation and electromagnetic radiation, which together can further be separated into four different channels, including SPP channel on the tip, SPP channel on the substrate, air mode channel and direct quenching channel. We find that most of the excited energy goes to surface plasmon polaritons on the metallic STM tip, rather than that on the substrate. The direct quenching in the apex of tip also takes a considerable portion especially in high frequency region.