Modeling of the gate-controlled Kondo effect at carbon point defects in graphene

Abstract

We study the magnetic properties in the vicinity of a single carbon defect in a monolayer of graphene. We include the unbound σ orbital and the vacancy induced bound π state in an effective two-orbital single impurity model. The local magnetic moments are stabilized by the Coulomb interaction as well as a significant ferromagnetic Hund's rule coupling between the orbitals predicted by a density functional theory calculation. A hybridization between the orbitals and the Dirac fermions is generated by the curvature of the graphene sheet in the vicinity of the vacancy. We present results for the local spectral function calculated using Wilson's numerical renormalization group approach for a realistic graphene band structure and find three different regimes depending on the filling, the controlling chemical potential, and the hybridization strength. These different regions are characterized by different magnetic properties. The calculated spectral functions qualitatively agree with recent scanning tunneling spectra on graphene vacancies.

Inducing Kondo screening of vacancy magnetic moments in graphene with gating and local curvature

“…3 ). Results from a comprehensive NRG calculation using a two-orbital pseudogap AIM to model the problem 38 similarly indicate that this simplified one-orbital approach qualitatively describes the experimental results. The single orbital AIM is characterized by three energy scales, ε d , U , and Γ 0 , corresponding to the energy of the impurity state, the onsite Coulomb repulsion, and by the scattering rate or exchange between the impurity and the conduction electrons, respectively (Supplementary Note 7 ).…”

Reentrant Kondo effect for a quantum impurity coupled to a metal-semiconductor hybrid contact

“…This AGNR+QI+STM system is particularly attractive, as Kondo physics in carbon-based materials, mainly in bulk samples, has attracted a great deal of attention in the last few years [19][20][21][22][23][24][25][26][27][28] . The Kondo physics in graphene results from localized magnetic moments formed at vacancy sites [29][30][31][32] or through the surface deposition of magnetic atoms 33,34 , in which the local density of states may be modified by either disorder 35,36 or by ripples induced by the underlying substrate 34 . Contrasting to the plethora of studies addressing the Kondo state in carbon nanotubes and on bulk graphene, less attention has been devoted to this effect in nanoribbon systems [37][38][39][40] .…”

Kondo holes in strongly correlated impurity arrays: RKKY driven Kondo screening and hole-hole interactions

“…Well studied examples are gaped or system with pseudo gap density of states [47]. In graphene, for example, carbon vacancies generated such single particle bound states [48][49][50] which are subject to Kondo screening [51,52]. In this paper, however, we focus on conventional metallic conduction band hosts, where such localized orbitals are induced by vacancies in dense systems called Kondo holes.…”