Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 105: Graphene: Bi- and Multi-Layers (organized by HL)

TT 105.5: Talk

Friday, April 4, 2014, 10:30–10:45, POT 081

RKKY interaction in the AB stacked graphene bilayer: interstitial impurities and a diverging propagator. — •Nicolas Klier, Sam Shallcross, and Oleg Pankratov — Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7B2, 91058 Erlangen

The interaction between spin polarised impurities in graphene displays a number of novel features that arise both from the valley degree of freedom that graphene possesses, as well as the linearly vanishing density of states at the Dirac point [1,2]. Multilayer graphene systems offer both the possibility of realistic interstitial (i.e., interlayer) impurities, as well as novel electronic features. In particular, the Bernal stacked (AB) bilayer exhibits low energy (chiral) bands as well as high energy bonding and anti-bonding bands. We demonstrate that at the bonding to anti-bonding gap edge there is an logarithmic divergence log(E−E_g) in the propagator on one sublattice, with E the energy and E_g the energy of the bonding to anti-bonding gap (0.38 eV). This leads to a number of dramatic consequences for the RKKY interaction, most notably: (i) a R^−5/2 impurity interaction at the gap edge, and, (ii) for interstitial impurities a discontinuous change in the Fermi surface spanning vector that drives the RKKY at the gap edge. We further derive the finite temperature behaviour of this system on the basis of finite temperature perturbation theory.

[1] M.Sherafati, and S.Satpathy, Phys. Rev. B 84, 125416, 2011.

[2] F.Parhizgar, and M.Sherafati, and R.Asgari, and S.Satpathy, Phys. Rev. B 87, 165429, 2013.