Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 53: Graphene (jointly with DY, DS, HL, MA, O)

TT 53.1: Vortrag

Donnerstag, 17. März 2011, 15:15–15:30, HSZ 401

Tunable edge magnetism in graphene — •Manuel J. Schmidt¹, Daniel Loss¹, David J. Luitz², and Fakher F. Assaad² — ¹Universität Basel, Switzerland — ²Universität Würzburg, Germany

Edge states with nearly zero energy that are exponentially localized at zigzag edges of graphene ribbons, in combination with electron-electron interactions give rise to edge magnetism. We show how the characteristic momentum-dependence of the transverse wave function of the edge states may be exploited in order to manipulate the edge state bandwidth [1]. This allows to tune graphene edges from the usual edge magnetism regime, over a regime of itinerant one-dimensional ferromagnetism, down to the non-magnetic Luttinger liquid regime. As an example we discuss graphene/graphane interfaces for which we propose an experimental setting in which the bandwidth may be tuned in situ by means of electrostatic gates [2]. We introduce an effective one-dimensional model for the edge states, on the basis of which we investigate the tunability of edge magnetism. Our analysis uses essentially three techniques: by a mean-field treatment of the effective interaction, the phase diagram is established. Quantum fluctuations, which may not be neglected in one dimension, are taken into account on the basis of a bosonization technique. Finally, these analytical calculations are complemented by an exact diagonalization analysis of the effective edge state model.

[1] M.J. Schmidt and D. Loss, Phys. Rev. B 81, 165439 (2010).

[2] M.J. Schmidt and D. Loss, Phys. Rev. B 82, 085422 (2010).