Vladimir Falko


Partial ordering of dilute adsorbents on graphene

Location: Dahlem Center Seminar Room
Time: Monday 25.01.2010, 16h c.t.

We investigate a possibility of formation of a correlated state in a dilute ensemble of adatoms randomly deposited on graphene. For the adsorbents that reside in the middle of hexagons of the honecomb graphene lattice, as well as for those that take position over the centre of the AB bond, we find a tendency towards a spatially correlated state with a hidden Kekule mosaic order. This effect emerges from the interaction between the adatoms mediated by the Friedel oscillations of the electron density in graphene. The problem is mapped onto the three-value random Potts model, and the critical temperature of the partial ordering transition is established using the cluster Monte-Carlo simulations. The onset of the ordered state, as the system is cooled below the critical temperature, is accompanied by an effective Brillouin zone folding and opening of a gap in the electronic spectrum. For the adsorbents which reside over carbon sites the corresponding partial ordering (similar to the ordering transition in a random Ising model with ferromagnetic coupling) would result in the A-B sublattice symmetry breaking, also leading to the spectral gap formation.


More information:  P. Brouwer e-mail  

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