Transport Characterization of Kondo-Correlated Single Molecule Devices

TL;DR

This study refines the understanding of Kondo effects in single molecule devices by accounting for background conductance, resolving previous inconsistencies and highlighting the significance of non-Kondo channels in transport measurements.

Contribution

It introduces a constrained analysis method that simultaneously considers conductance dependence on temperature, bias, and magnetic field, clarifying the role of non-Kondo contributions.

Findings

Proper background conductance accounting resolves numerical inconsistencies.

Non-Kondo channels significantly influence transport in high-conductance devices.

Demonstrates the importance of comprehensive analysis for accurate Kondo state characterization.

Abstract

A single molecule break junction device serves as a tunable model system for probing the many body Kondo state. The low-energy properties of this state are commonly described in terms of a Kondo model, where the response of the system to different perturbations is characterized by a single emergent energy scale, k_B*T_K. Comparisons between different experimental systems have shown issues with numerical consistency. With a new constrained analysis examining the dependence of conductance on temperature, bias, and magnetic field simultaneously, we show that these deviations can be resolved by properly accounting for background, non-Kondo contributions to the conductance that are often neglected. We clearly demonstrate the importance of these non-Kondo conduction channels by examining transport in devices with total conductances exceeding the theoretical maximum due to Kondo-assisted tunneling alone.