Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 12: Graphene: mostly Theory (with O/TT)

HL 12.5: Talk

Monday, March 16, 2015, 16:00–16:15, ER 164

Magnetic interactions in bilayer graphene — •Nicolas Klier, Sam Shallcross, and Oleg Pankratov — Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7B2, 91058 Erlangen

The indirect exchange interaction between magnetic impurities, known as the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, is governed by the static spin susceptibility of the host system and therefore depends sensitively on the host electronic structure. For this reason, this interaction is particularly interesting for materials in which the underlying electronic spectrum is novel, such as single layer and bilayer graphene. We investigate the RKKY interaction for bilayer graphene at zero and at finite temperature, as well as for the case in which the bilayer is biased by a perpendicular electric field. At the edge of the energy gap between the two conduction (or valence) bands at the Dirac point we find a remarkable transition in the form of the RKKY interaction. For Fermi energies on either side of the gap the interaction takes asymptotically two different forms: the oscillatory or the anti-ferromagnetic. We show that at the Dirac point the sign of the RKKY interaction (ferromagnetic vs anti-ferromagnetic) can be controlled by an external electric field.