Surface imaging of inelastic Friedel oscillations

TL;DR

This paper proposes using STM to image inelastic Friedel oscillations caused by vibrational modes of surface impurities, revealing inelastic scattering effects through second derivative current measurements.

Contribution

It introduces a method to detect inelastic scattering from vibrational impurity modes via imaging $rac{ ext{d}^2I}{ ext{d}V^2}$ oscillations, linking vibrational modes to Friedel-like surface oscillations.

Findings

Vibrational modes induce Friedel oscillations in $rac{ ext{d}^2I}{ ext{d}V^2}$.

STM imaging can visualize inelastic scattering effects.

Inelastic Friedel oscillations are analogous to screening charge oscillations.

Abstract

Impurities that are present on the surface of a metal often have internal degrees of freedom. Inelastic scattering due to impurities can be revealed by observing local features seen in the tunneling current with scanning tunneling microscope (STM). We consider localized vibrational modes coupled to the electronic structure of a surface. We argue that vibrational modes of impurities produce Fermi momentum $k_F$ oscillations in second derivative of current with respect to voltage $\partial^2I(\br, V)/\partial V^2$. These oscillations are similar to the well known Friedel oscillations of screening charge on the surface. We propose to measure inelastic scattering generated by the presence of the vibrational modes with STM by imaging the $\partial^2I/\partial V^2$ oscillations on the metal surface.