Gate controlled quantum interference: direct observation of anti-resonances in single molecule charge transport

TL;DR

This study demonstrates direct observation and control of quantum interference effects, including anti-resonances, in single molecule charge transport using electrochemical gating, revealing potential for high-speed, low-power electronic applications.

Contribution

It introduces a method to probe and tune quantum interference in single molecules across a broad energy range, directly observing anti-resonances and controlling conductance over large ranges.

Findings

Direct observation of anti-resonance in single molecule conductance.

Electrochemical gating enables tuning of quantum interference effects.

Achieved conductance modulation over two orders of magnitude.

Abstract

Quantum interference can profoundly affect charge transport in single molecules, but experiments can usually measure only the conductance at the Fermi energy. Because in general the most pronounced features of the quantum interference are not located at the Fermi energy, it is highly desirable to probe charge transport in a broader energy range. Here by the method of electrochemical gating, we measure the conductance and map the transmission functions of single molecules at and around the Fermi energy, and study signatures associated with constructive and destructive interference. With the electrochemical gate control, we tune the quantum interference between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), and directly observe anti-resonance, a distinct feature of destructive interference. By tuning the molecule in and out of anti-resonance, we achieve continuous control of the conductance over 2 orders of magnitude with a subthreshold swing of ~17 mV/dec, features relevant to high-speed and low-power electronics.