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Phys. Rev. Lett. 101, 246404 (2008) [4 pages]

Vortices, Zero Modes, and Fractionalization in the Bilayer-Graphene Exciton Condensate

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B. Seradjeh1, H. Weber1,2, and M. Franz1
1Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
2Institut für Theoretische Physik, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

Received 4 June 2008; published 12 December 2008

A real-space formulation is given for the recently discussed exciton condensate in a symmetrically biased graphene bilayer. We show that in the continuum limit an oddly quantized vortex in this condensate binds exactly one zero-mode per valley index of the bilayer. In the full lattice model, the zero modes are split slightly due to intervalley mixing. We support these results by an exact numerical diagonalization of the lattice Hamiltonian. We also discuss the effect of the zero modes on the charge content of these vortices and deduce some of their interesting properties.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.101.246404
DOI:
10.1103/PhysRevLett.101.246404
PACS:
71.35.−y, 71.10.Pm, 73.20.Mf