Kondo blockade due to quantum interference in single-molecule junctions

• Published in: Nature communications Vol. 8; no. 1; p. 15210
• Main Authors: Mitchell, Andrew K., Pedersen, Kim G. L., Hedegård, Per, Paaske, Jens
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.05.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/1130/2798; 639/766/119/1001; 639/766/119/998; Electrons; Humanities and Social Sciences; multidisciplinary; Physics; Quantum dots; Science; Science (multidisciplinary); Denmark
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms15210

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. Exploring the interplay of quantum effects enriches the scientific and technological understanding in nanoscale devices. The authors find that two apparently different quantum effects, quantum interference and the Kondo effect, can be unified to describe electron transport in single-molecule junctions.