Hysteresis phenomena in electron tunneling, induced by surface plasmons

TL;DR

This study investigates hysteresis phenomena in electron tunneling caused by localized surface plasmons on gold surfaces, revealing non-classical properties and potential explanations involving double well potentials.

Contribution

It introduces the observation of hysteresis in tunneling signals induced by surface plasmons and suggests a new explanation involving multiple image charge effects.

Findings

Hysteresis in tunnel current depends on bias direction.

Double well potential explains hysteresis behavior.

Hysteresis loop area shows stepwise changes.

Abstract

A high spatial resolution surface plasmon near field scanning tunneling microscope (STM) has been used to study the properties of localized surface plasmons (SPO) in so-called hot spots on a gold surface, where the local electromagnetic field is extremely high. A CW semiconductor laser and a femtosecond Ti:Sa laser were used to excite the plasmons and the SPO excited tunnel current was used as the detector. When scanning the STM from negative to positive bias and reversed, hysteresis in the tunnel signal was found, excluding (or rather minimizing) the role of the presence of a Casimir effect in the process. It was found, however, that a multiple image charge induced double well potential may explain our experimental findings. The stepwise behaviour of the area of the observed hysteresis loops is a new, additional indication of the non-classical properties of the SPOs.