# Dresden 2014 – wissenschaftliches Programm

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# O: Fachverband Oberflächenphysik

## O 19: Graphene: Structural properties

### O 19.12: Vortrag

### Montag, 31. März 2014, 18:45–19:00, WIL C107

**Improved effective theories for edge magnetism** — •Cornelie Koop and Manuel Schmidt — Institut für Theoretische Festkörperphysik, RWTH Aachen University, Deutschland

We consider the effective interaction between edge states in graphene nanoribbons. Low-energy edge states come along with a strongly enhanced density of states near the graphene edges, which makes electron-electron correlation important and gives rise to the so-called edge magnetism. In a pristine nanoribbon in first order, there is a direct ferromagnetic intra-edge coupling and an antiferromagnetic interaction between opposite edges. We study the coupling by means of an effective model yielding a separation between edge and bulk states. In particular we investigate the influence of the bulk states on the effective edge state theory via a second order Schrieffer-Wolff transformation. Using both numeric and analytic methods, we calculate various correlation functions. We discuss the results for the effective correlations between smooth edges as well as between the strongly localized states at rough edge structures.