Controlled Contact to a C60 Molecule

TL;DR

This study investigates the conductance behavior of a C60 molecule on Cu(100) using low-temperature STM, revealing conductance jumps and the influence of structural fluctuations during contact formation.

Contribution

It provides new insights into the conductance transition from tunneling to contact for C60 molecules, supported by combined experimental and theoretical analysis.

Findings

Conductance rapidly rises to 0.25 G0 at the tunneling-contact transition.

Abrupt jump to G0 observed with decreasing tip-molecule distance.

Structural fluctuations significantly influence conductance in the contact regime.

Abstract

The conductance of C60 on Cu(100) is investigated with a low-temperature scanning tunneling microscope. At the transition from tunneling to the contact regime the conductance of C60 adsorbed with a pentagon-hexagon bond rises rapidly to 0.25 conductance quanta G0. An abrupt conductance jump to G0 is observed upon further decreasing the distance between the instrument's tip and the surface. Ab-initio calculations within density functional theory and non-equilibrium Green's function techniques explain the experimental data in terms of the conductance of an essentially undeformed C60. From a detailed analysis of the crossover from tunneling to contact we conclude that the conductance in this region is strongly affected by structural fluctuations which modulate the tip-molecule distance.