The Kondo effect in C$_{60}$ single-molecule transistors

TL;DR

This paper reports the fabrication and characterization of C60 single-molecule transistors, demonstrating the Kondo effect with high Kondo temperatures and vibrational mode signatures persisting into the Kondo regime.

Contribution

It introduces a fabrication protocol for C60 transistors and provides experimental evidence of the Kondo effect at relatively high temperatures.

Findings

Observation of Kondo effect with T_K > 50 K

Detection of vibrational modes in the Kondo regime

Successful fabrication of single-molecule transistors

Abstract

We have used an electromigration technique to fabricate C$_{60}$-based single-molecule transistors. We detail the process statistics and the protocols used to infer the successful formation of a single-molecule transistor. At low temperatures each transistor acts as a single-electron device in the Coulomb blockade regime. Resonances in the differential conductance indicate vibrational excitations consistent with a known mode of C$_{60}$. In several devices we observe conductance features characteristic of the Kondo effect, a coherent many-body state comprising an unpaired spin on the molecule coupled by exchange to the conduction electrons of the leads. The inferred Kondo temperature typically exceeds 50 K, and signatures of the vibrational modes persist into the Kondo regime.