Quantum-interference-controlled three-terminal molecular transistors based on a single ring-shaped-molecule connected to graphene nanoribbon electrodes

TL;DR

This paper investigates three-terminal molecular transistors based on a ring-shaped molecule connected to graphene nanoribbon electrodes, demonstrating quantum interference effects that enable transistor switching and current control via dephasing and gate voltage.

Contribution

It introduces a novel all-carbon molecular transistor design utilizing quantum interference and dephasing effects, analyzed with advanced nonequilibrium Green function and DFT methods.

Findings

Destructive interference leads to exponentially small transmission.

Dephasing via a third electrode switches the device to an 'on' state.

Gate voltage effectively controls current in the 'on' regime.

Abstract

We study all-carbon-hydrogen molecular transistors where zigzag graphene nanoribbons play the role of three metallic electrodes connected to a ring-shaped 18-annulene molecule. Using the nonequilibrium Green function formalism combined with density functional theory, recently extended to multiterminal devices, we show that the proposed nanostructures exhibit exponentially small transmission when the source and drain electrodes are attached in a configuration that ensures destructive interference of electron paths around the ring. The third electrode, functioning either as an attached infinite-impedance voltage probe or as an "air-bridge" top gate covering half of molecular ring, introduces dephasing that brings the transistor into the "on" state with its transmission in the latter case approaching the maximum limit for a single conducting channel device. The current through the latter device can also be controlled in the far-from-equilibrium regime by applying a gate voltage.