Theory of a benzene transistor: symmetry, strong correlations and quantum interference*

Single molecule transistors offer a fascinatingly diverse range of physics beyond the capabilities of Si transistors. Their ultrasmall size, chemical complexity, and electronic interactions constitute a unique playground for exploring the fundamental physics of correlations on the nanoscale, and their transport signatures. Understanding these systems is an essential prerequisite for possible advanced technological applications utilizing their quantum characteristics. In this talk I examine the interplay of symmetry and Kondo effect in a benzene single electron transistor using a combination of numerical renormalization group and generalised Schrieffer Wolff transformation [1]. Depending on the connectivity of the leads and gate voltages, we uncover spin-1/2 and spin-1 Kondo effects, a quantum phase transition to a state with robust molecular magnetism, and destructive quantum interference at an emergent SU(4) symmetry point. The interplay between emergent many-body effects and molecular symmetry is discussed in the context of quantum-boosted device functionality.

1. Kondo blockade due to quantum interference in single-molecule junctions. Nat Commun 8, 15210 (2017)