Manifestation of the shape and edge effects in spin-resolved transport through graphene quantum dots

TL;DR

This paper presents a theoretical study of how the shape and edge magnetization of graphene quantum dots influence spin-resolved transport properties, revealing phenomena like negative differential conductance and complex TMR behavior.

Contribution

It introduces a detailed theoretical analysis of shape and edge effects on transport in graphene quantum dots using exact diagonalization and diagrammatic techniques.

Findings

Shape-dependent negative differential conductance observed.

Edge magnetization significantly affects TMR and shot noise.

Transport characteristics vary with quantum dot geometry.

Abstract

We report on theoretical studies of transport through graphene quantum dots weakly coupled to external ferromagnetic leads. The calculations are performed by exact diagonalization of a tight-binding Hamiltonian with finite Coulomb correlations for graphene sheet and by using the real-time diagrammatic technique in the sequential and cotunneling regimes. The emphasis is put on the role of graphene flake shape and spontaneous edge magnetization in transport characteristics, such as the differential conductance, tunneling magnetoresistance (TMR) and the shot noise. It is shown that for certain shapes of the graphene dots a negative differential conductance and nontrivial behavior of the TMR effect can occur.