Coulomb Blockade in Graphene Nanodisks

TL;DR

This paper studies Coulomb blockade phenomena in graphene nanodisks, revealing unique electron interaction effects and spectral features due to the nanodisk's zero-energy states and lack of SU(N) symmetry.

Contribution

It derives explicit electron-electron interactions in graphene nanodisks and analyzes their Coulomb blockade behavior using Green function methods, uncovering novel spectral features.

Findings

Observation of peculiar occupation number plateaux and dips.

Identification of Coulomb correlation effects causing dips.

Revelation of energy spectrum structure without SU(N) symmetry.

Abstract

Graphene nanodisk is a graphene derivative with a closed edge. The trigonal zigzag nanodisk with size $N$ has $N$-fold degenerated zero-energy states. We investigate electron-electron interaction effects in the zero-energy sector. We explicitely derive the direct and exchange interactions, which are found to have no SU($N$) symmetry. Then, regarding a nanodisk as a quantum dot with an internal degree of freedom, we analyze the nanodisk-lead system consisting of a nanodisk and two leads. Employing the standard Green function method, we reveal novel Coulomb blockade effects in the system. The occupation number in the nanodisk exhibits a peculiar series of plateaux and dips, reflecting a peculiar structure of energy spectrum of nanodisk without SU($N$) symmetry. Dips are argued to emerge due to a Coulomb correlation effect.