Kondo blockade due to quantum interference in single-molecule junctions

TL;DR

This paper demonstrates how quantum interference and the Kondo effect interact in single-molecule junctions, revealing conditions for conductance enhancement or blockade, and provides a systematic framework for understanding these phenomena.

Contribution

It unifies quantum interference and Kondo effects in molecular electronics, offering an exact theoretical framework to analyze their interplay and resulting transport properties.

Findings

Kondo-mediated conductance nodes from destructive interference

Gate-tunable conductance peaks and nodes

Nonstandard temperature dependence of conductance

Abstract

Molecular electronics offers unique scientific and technological possibilities, resulting from both the nanometre scale of the devices and their reproducible chemical complexity. Two fundamental yet different effects, with no classical analogue, have been demonstrated experimentally in single-molecule junctions: quantum interference due to competing electron transport pathways, and the Kondo effect due to entanglement from strong electronic interactions. Here we unify these phenomena, showing that transport through a spin-degenerate molecule can be either enhanced or blocked by Kondo correlations, depending on molecular structure, contacting geometry and applied gate voltages. An exact framework is developed, in terms of which the quantum interference properties of interacting molecular junctions can be systematically studied and understood. We prove that an exact Kondo-mediated conductance node results from destructive interference in exchange-cotunneling. Nonstandard temperature dependences and gate-tunable conductance peaks/nodes are demonstrated for prototypical molecular junctions, illustrating the intricate interplay of quantum effects beyond the single-orbital paradigm.