Theory of a Scanning Tunneling Microscope with a Two-Protrusion Tip

TL;DR

This paper develops a theoretical model for a scanning tunneling microscope with a two-protrusion tip, analyzing how it probes electronic transport and impurity potentials on surfaces, which is relevant for advanced surface characterization.

Contribution

It introduces a theoretical framework for understanding STM measurements with two-protrusion tips, highlighting their potential for probing local electronic properties and impurity dynamics.

Findings

Differential conductance depends on transport between the protrusions.

Two-protrusion tips can probe impurity potentials and local transport.

Model aids in interpreting STM data with complex tip geometries.

Abstract

We consider a scanning tunneling microscope (STM) such that tunneling occurs through two atomically sharp protrusions on its tip. When the two protrusions are separated by at least several atomic spacings, the differential conductance of this STM depends on the electronic transport in the sample between the protrusions. Furthermore two-protrusion tips commonly occur during STM tip preparation. We explore possible applications to probing dynamical impurity potentials on a metallic surface and local transport in an anisotropic superconductor.