Quasi-Phase Transition and Many-Spin Kondo Effects in Graphene Nanodisk

Abstract

The trigonal zigzag nanodisk with size $N$ has $N$ localized spins. We investigate its thermodynamical properties with and without external leads. Leads are made of zigzag graphene nanoribbons or ordinary metallic wires. There exists a quasi-phase transition between the quasi-ferromagnet and quasi-paramagnet states, as signaled by a sharp peak in the specific heat and in the susceptability. Lead effects are described by the many-spin Kondo Hamiltonian. A new peak emerges in the specific heat. Furthermore, the band width of free electrons in metallic leads becomes narrower. By investigating the spin-spin correlation it is argued that free electrons in the lead form spin-singlets with electrons in the nanodisk. They are indications of many-spin Kondo effects.

arXiv comment5 pages, 5 figures

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• Probing local moments in nanographenes with electron tunneling spectroscopy
• Generation and Manipulation of Spin Current in Graphene Nanodisks: Robustness against Randomness and Lattice Defects
• Study of decoherence in models for hard-core bosons coupled to optical phonons
• Kondo effect in Lieb's ferrimagnetic system on the T-shaped bipartite lattice