Tunable Fano resonance in a parallelly coupled diatomic molecular transistor

TL;DR

This paper explores how electron transport through a diatomic molecular transistor exhibits tunable Fano resonances influenced by Coulomb interactions, revealing how these interactions modify resonance shapes and positions.

Contribution

It introduces a model incorporating Hubbard interactions and complex source-sink potentials to analyze Fano resonance behavior in molecular transistors.

Findings

Fano lineshape appears as Hubbard interaction is introduced.

Fano lineshape broadens and shifts with increasing U, eventually disappearing.

The Breit-Wigner resonance persists but shifts and narrows at high U.

Abstract

We investigate electron transport through a diatomic molecule parallelly coupled to infinite source and drain contacts. We utilize a model Hamiltonian involving a Hubbard term in which the contacts are modeled using recently developed complex source and sink potentials. The zero bias transmission spectrum for a symmetrically coupled system as a function of the Fermi energy acquires a Fano lineshape as the Hubbard interaction is turned on. For large values of $U$, the Fano lineshape broadens and shifts to higher energy values disappearing eventually. Meanwhile, the Breit-Wigner resonance located at the bonding resonance in the noninteracting limit survives but its position is shifted twice the coupling between the atoms in the molecule in the infinite $U$ limit and its linewidth is reduced to half. We attribute this behaviour to the unavailability of one of the transmission channels due to Coulomb blockade.