Title: Equilibrium currents in a Corbino graphene ring
Author(s):

	A. López (Centro de Física, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020A, Venezuela) ,
	N. Bolívar (Centro de Física, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020A, Venezuela; Statistical Physics Group, P2M Department, Institut Jean Lamour, UMR CNRS 7198, BP 70239 F-54506 Vand\oe uvre les Nancy Cedex, France ; Departamento de Física, Universidad Central de Venezuela, Caracas, Venezuela) ,
	E. Medina (Centro de Física, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020A, Venezuela; Statistical Physics Group, P2M Department, Institut Jean Lamour, UMR CNRS 7198, BP 70239 F-54506 Vand\oe uvre les Nancy Cedex, France; Departamento de Física, Universidad Central de Venezuela, Caracas, Venezuela) ,
	B. Berche (Centro de Física, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020A, Venezuela; Statistical Physics Group, P2M Department, Institut Jean Lamour, UMR CNRS 7198, BP 70239 F-54506 Vand\oe uvre les Nancy Cedex, France )

We address the description of a graphene Corbino disk in the context of a tight binding approach that includes both kinetic and Rashba spin-orbit coupling due to an external out-of-plane electric field. Persistent equilibrium currents are induced by an external magnetic field breaking time reversal symmetry. By direct diagonalization, we compute the spectrum and focus on the dispersion near the K points at the Fermi level. The dispersion keenly reproduces that of a continuum model in spite of the complexity of the boundary conditions. We validate the assumptions of the continuum model in terms of predominant zig-zag boundaries conditions and weak sub-band coupling. The wave functions displaying the lowest transverse modes are obtained, showing the predominance of edge states with charge density at the zig-zag edges. The persistent charge currents, nevertheless, do not follow the traditional argument of current cancellation from levels below the Fermi level, and thus they depart in the tight-binding from those found in the continuum model.

Key words: tight-binding Hamiltonian, graphene, spin-orbit interaction, charge and spin transport
PACS: 85.75.-d, 03.65.Vf

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