Graphene armchair nanoribbon single-electron transistors: The peculiar influence of end states

TL;DR

This paper develops a microscopic theory for graphene nanoribbon quantum dots, revealing how long and short-range interactions influence electronic properties, leading to unique entangled states and negative differential conductance effects.

Contribution

It introduces a detailed microscopic model that explains the role of interactions and lattice effects in end states and transport phenomena in graphene nanoribbon quantum dots.

Findings

Long-range interactions cause Coulomb blockade and spin-charge separation.

Short-range interactions induce exchange correlations and entanglement between end and bulk states.

Negative differential conductance arises from symmetry-forbidden transitions in the system.

Abstract

We present a microscopic theory for interacting graphene armchair nanoribbon quantum dots. Long range interaction processes are responsible for Coulomb blockade and spin-charge separation. Short range ones, arising from the underlying honeycomb lattice of graphene, smear the spin-charge separation and induce exchange correlations between bulk electrons - delocalized on the ribbon - and single electrons localized at the two ends. As a consequence, entangled end-bulk states where the bulk spin is no longer a conserved quantity occur. Entanglement's signature is the occurrence of negative differential conductance effects in a fully symmetric set-up due to symmetry-forbidden transitions.