Kondo Effect in Graphene Nanoribbons with Magnetic Impurities*

In this work we have performed a detailed analysis of the Kondo effect of a magnetic impurity in graphene nanoribbons with zigzag edge termination [1]. We have considered an adatom coupled to the graphene nanoribbon via a hybridization amplitude in two different configurations: hollow or top site. In addition, the adatom is also weakly coupled to a metallic STM tip by a hybridization function that provides a Kondo screening of its magnetic moment. We have described the entire system by the well-known Anderson-like Hamiltonian [2] whose low-temperature physics is accessed by employing the numerical renormalization group approach [3], which allows us to obtain the thermodynamic properties used to compute the Kondo temperature of the system. In our numerical calculation, two screening regimes were observed: local singlet and Kondo singlet, which strongly depends on the impurity adatom location and on the coupling strength of the carbon sites of the graphene nanoribbon with the adatom impurity.

[1] G. S. Diniz, G. I. Luiz, A. Latgé, and E. Vernek. Phys. Rev. B 97, 115444 (2018).
[2] P. W. Anderson, Phys. Rev. 124, 41 (1961).
[3] K. G. Wilson, Rev. Mod. Phys. 47, 773 (1975).