Kondo effect in bilayer graphene

D. MASTROGIUSEPPE; S. ULLOA; N. SANDLER

Davidson College, NC

Conferencia; Chemistry & Physics of Graphitic Carbon Materials; 2012

Gordon Research Conference

Motivated by recent theoretical and experimental work on the role of magnetic impurities on graphene, in which the Dirac nature of the low energy electrons lead to certain peculiarities in the Kondo effect [1], we address the problem of a magnetic impurity intercalated in bilayer graphene in the Bernal stacking. Compared to the single layer case bilayer graphene has an extra degree of freedom, the interlayer hopping t_p. Although the linearity of the bands around the neutrality points is lost when this coupling is present, the four-band nature of the energy dispersion in this material gives rise to a feature in the density of states which manifests as a jump when E = ±t_p. We describe the system starting with a multiband Anderson model and obtaining an effective Kondo model through the Schrieffer-Wolff transformation [2]. We show that under particular hybridizing configurations between the impurity and the band electrons, the model presents a quantum phase transition when the chemical potential crosses over the energy t_p, allowing for a tunable Kondo effect.