Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

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

HL 12.4: Talk

Monday, March 16, 2015, 15:45–16:00, ER 164

Controlling the localization of electrons in bilayer graphene — •Maximilian Fleischmann, Sam Shallcross, and Oleg Pankratov — Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7B2, 91058 Erlangen

Two mutually rotated layers of graphene exhibit an electronic structure that depends profoundly on the rotation angle. The small angle regime in particular is associated with significant changes of the electronic properties of the bilayer: one finds localization on the moiré lattice and a significant reduction in the Fermi velocity near the Dirac point [1]. We investigate how the electronic properties in the small angle limit may be controlled by an external electric field directed perpendicular to the bilayer. We consider a uniform field as well as modulated fields with a period chosen to “connect” the Dirac cones of the two layers in momentum space. The latter electrostatic potentials may be realized by a proper choice of substrate. We find that electric fields can be used to control the degree of localization of the quasiparticles in the bilayer. A uniform field tends to delocalize the electron states; this effect is generally less pronounced for energies close to the Dirac point. In contrast, a modulated field favours electron localization throughout the low-energy spectrum.

[1] S. Shallcross et al., Phys. Rev. B 87, 245403, 2013.