Topographical fingerprints of many-body interference blocking in STM junctions on thin insulating films

TL;DR

This paper investigates how interference effects cause negative differential conductance in molecular junctions, proposing a criterion to identify interference blocking through combined spectral and topographical STM measurements, supported by simulations.

Contribution

It introduces a new criterion to detect interference blocking in STM measurements, linking spectral and topographical data for molecules on insulating films.

Findings

Simulation of CuPc on thin film shows characteristic NDC behavior.

Correlation between spectral features and topographical maps reveals interference effects.

Proposed criterion can guide experimental identification of interference blocking.

Abstract

Negative differential conductance (NDC) is a non-linear transport phenomenon ubiquitous in molecular nanojunctions. Its physical origin can be the most diverse. In rotationally symmetric molecules with orbitally degenerate many-body states, it can be ascribed to interference effects. We establish in this paper a criterion to identify the interference blocking scenario by correlating the spectral and the topographical information achievable in an STM single molecule measurement. Simulations of current voltage characteristics and current maps for a Cu-Phthalocyanine (CuPc) on a thin insulating film are presented as experimentally relevant examples.