Abstract
We discuss a role of the localized π orbital, which exists around the defect, on the defect-induced Kondo effect in graphene by a numerical renormalization group study. We find that the localized π orbital assists this Kondo effect, and the Kondo temperature is sensitive to the broadening of the localized π orbital. Secondly, we focus on the negative magnetoresistance of this Kondo effect. In the experimental result, it has been shown that the negative magnetoresistance is ten times larger than the usual Kondo effect. In order to clarify the mechanism of the ’’magnetic sensitive” Kondo effect, as a first step, we study an orbital magnetic field dependence of the localized n orbital by a tight-binding model with a Peierls phase. We find that as the magnetic field increases, the spectral width of the localized π orbital increases and the local DOS at the Fermi level decreases. Since the Kondo temperature is strongly dependent of the broadening of the localized π orbital, it is expected that this Kondo effect is sensitive to the orbital magnetic field as observed in the experiment.
Highlights
After the fabrication of graphene, the Kondo effect in graphene has attracted much theoretical attention, because exotic Kondo effects and associated phenomena due to its Dirac conduction electrons are expected, such as multichannel Kondo effects, gate-tunable Kondo effects, and an impurity quantum phase transition between an unscreened and a screened localized moment state [1,2,3,4,5,6].As candidates of the realization of the Kondo effect in graphene, the graphene with magnetic impurities such as Fe or Co has been investigated by DFT calculations [2]
We find that the localized π orbital assists the Kondo effect, and the Kondo temperature is sensitive to the broadening of the localized π orbital
In order to clarify the mechanism of the magnetic sensitive Kondo effect, as a first step, we study an orbital magnetic field dependence of the localized π orbital by a tight-binding model with a Peierls phase
Summary
After the fabrication of graphene, the Kondo effect in graphene has attracted much theoretical attention, because exotic Kondo effects and associated phenomena due to its Dirac conduction electrons are expected, such as multichannel Kondo effects, gate-tunable Kondo effects, and an impurity quantum phase transition between an unscreened and a screened localized moment state [1,2,3,4,5,6].As candidates of the realization of the Kondo effect in graphene, the graphene with magnetic impurities such as Fe or Co has been investigated by DFT calculations [2]. A model where the localized state of π electrons is rather artificially added at the defect [10, 15] has been proposed, more consideration on the derivation of the model and the analysis are necessary In this defect induced Kondo effect, the anomalous negative magnetoresistance has been observed: In the usual Kondo effect, the energy scale of a characteristic magnetic field of the negative magnetoresistance is the same order as that of the Kondo temperature. In order to clarify the mechanism of the magnetic sensitive Kondo effect, as a first step, we study an orbital magnetic field dependence of the localized π orbital by a tight-binding model with a Peierls phase. In §.4, we discuss an orbital magnetic field dependence of the localized state of π electrons by the tight binding model with the Peierls phase
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